Benny and Adrian Wall are on their way to the planet Rhinvil, which is unoccupied apart from the former actor Bratheen Traloor. Very little is known about the planet, which is why Traloor chose it for his retirement; however, while building a new extension for Traloor's mansion, Adrian's crew unearthed an unusual stone artefact, and Traloor has invited Benny to take a look at it. The journey is tense, as Benny is pointedly trying to avoid talking about what recently happened between her and Adrian -- or rather, what happened between Adrian and the alien sorceress who had possessed Benny's body at the time. As their shuttle enters the atmosphere, it is jolted by a surprisingly fierce storm, which almost seems to be trying to bring them down deliberately. They fly through it, and emerge over Traloor's mansion, but to Adrian's surprise, all of the expensive earth-moving equipment has been left out in the rain and there's no sign of his workers. Benny's flippancy about the missing workers angers Adrian, and she realises that she's being too hard on him. She checks out the marvellous ocean view while Adrian tries to get the equipment under cover, but experiences a strange dizzy sensation, and almost goes over the cliff before Traloor arrives and pulls her back from the edge...

Traloor takes his guests to the mansion, where House's mainframe -- an artificial intelligence with a somewhat familiar female voice -- has prepared rooms for them. He is far more pleasant to Benny than to Adrian, however; as far as he's concerned Adrian's men are charlatans, who have disrupted his solitude for weeks, only to begin vandalising his home before taking off without a word of warning. Adrian is offended by what Traloor is implying, but Traloor only backs down when Benny intervenes on Adrian's behalf. He is forced to admit that two of the men apparently vanished mysteriously some time before the others went; perhaps there is some other explanation for their disappearance. Traloor hasn't had to concern himself with the affairs of others for several years, and he thus apologises for his lack of tact. They will be housebound while the storm rages outside, but tomorrow they can begin to investigate. In the meantime, Adrian and Benny change for dinner; House, which refers to itself as Traloor's companion, has supplied Benny with an expensive wardrobe at Traloor's request. Adrian isn't satisfied with Traloor's claims, as he's sure that his men would never abandon their job half-finished. And as he and Benny set off for dinner, they hear a strange noise in the corridor, and Benny hears the distant sound of a woman sobbing...

Traloor has prepared dinner himself; he lives alone, apart from House, which he also refers to as his companion, and which he has modified extensively over the years as a hobby. But he's far more interested in talking about Benny's life than his own reclusive one. He and Adrian both understand Benny well enough to know she's itching to take a look at the artefact, and thus Traloor invites Benny to his study while Adrian amuses himself with the drinks cabinet. Benny is impressed by Traloor's collection; having spent too much time out in the harsh, ugly universe, he now chooses to surround himself with beauty. Benny concludes that the artefact is similar to other artefacts found near the Kar-Charrat system, but before she can study it more closely Adrian bursts in, shaken; while searching for the wine cellar, he was plunged into darkness, and heard the sound of a woman sobbing in the distance. He then heard Benny calling out to him, leading him on through the dark... but she's been here all along. Oddly, House has no record of a power failure in its systems log, but Traloor promises to run a diagnostic in the morning. Benny and Adrian retire for the night, but Benny is irritated with Adrian for interrupting her talk with Traloor... and is enraged when he enters her room later that night, apparently under the impression that she'd invited him. Deeply hurt by her extremely emphatic rejection, he storms back to his room -- and the unsettled Benny then hears more strange noises in the distance...

The next day, Benny heads out to the beach to study the area where the artefact was found, and spots a set of caves in the cliff from which the stone for the mansion was quarried. Traloor prefers to build from the stuff of this world, rather than contaminate the otherwise unspoiled Rhinvil with material from off-planet. He prefers the solitude to the complications and compromises brought on by having other people in one's life, but he also appreciates Benny's zest for life and her youthful energy. Flattered despite herself, Benny invites Traloor to visit the Collection, and he agrees to consider doing so. As another storm approaches, they return to the mansion, just as Adrian sets off to investigate the disappearances. As Traloor unlocks his study for Benny, Adrian tries to apologise to her for the previous night, although she really doesn't want to talk about it. He does, however, insist that he really did hear her voice inviting him into her room... and if it wasn't her speaking, then who was it?

Benny pops back to her room to change, and is irritated when Adrian calls her again insisting that she join him at the building site. She refuses, and tries to leave the room -- only to find the door jammed shut and hear a woman crying in the distance. The door finally opens, and Benny returns to the study begin her examination of the artefact. Traloor prepares breakfast, and takes coffee to Adrian, who has found some disturbing things at the building site. All of his friends' clothing and tools are still there, and their food is rotting where they left it; furthermore, the survey scanner is giving some very strange readings. Adrian doesn't mention these to Traloor, but he does note that Traloor seems a little too interested in talking about Benny. Traloor returns to the house, checks in on Benny once more, and orders the mainframe to run a self-diagnostic on itself. It seems almost reluctant to do so at first, inquires whether his guests will be staying long, and tells him that it's nice they can spend time together...

As Benny studies the artefact, Adrian arrives to ask for help, but when she complains about the continual interruptions he claims that he didn't phone her earlier. She reluctantly follows him to the building site, where she too is surprised by the readings which Adrian took earlier. It seems that the workers' shuttle is still here, which means that the workers must still be on the planet... but the shuttle is buried ten feet below ground, and the rocks show no signs of disturbance. It's as if the shuttle just sank down through the rock by itself. When Traloor arrives, looking for Benny, the confused and angry Adrian lashes out, accusing him of murder. Benny furiously intercedes, orders them both to calm down, and storms back to the study. She has just determined that the artefact is made of the same sedimentary limestone as the cliffs and mansion when the lights go out, and Adrian's voice speaks to her from the darkness, telling her that they must leave. But as his voice becomes more demanding and strident, she realises that this isn't Adrian speaking at all -- especially when the voice breaks down sobbing, the sound of a woman in torment...

Benny, seriously unnerved, goes to Adrian's rooms and admits that he was right; something weird is going on here. The female voice screams at them to leave, and this time they're willing to do so -- but when the voice realises that Benny intends to "rescue" Traloor as well, all hell breaks loose. The doors to the room lock by themselves and objects begin to fly about of their own accord. Adrian shoots out the door with his survey laser, and he and Benny flee into the corridors, forced to carry makeshift torches to find their way about. Meanwhile, Traloor is startled when the mansion is plunged into darkness, and demands answers from House. All it will tell him, however, is that he personally is in no danger, and that it is taking care of Benny and Adrian itself...

Benny and Adrian search for Traloor, but find something rather more disturbing -- his private rooms, which have been made over into something like a shrine devoted to Benny. When Traloor arrives to warn them about House, he realises he's been caught out; his interest in Benny is in fact obsession. As House screams at Benny, lashing out and breaking down into sobbing, Traloor is forced to point out what Adrian and Benny had failed to notice; House's voice is similar to Benny's own voice, as Traloor pieced it together from tapes of her lectures but didn't get the nuances quite right. Ever since he cut himself off from the rest of the Universe, Traloor has regarded Benny as an inspiration, a kindred spirit; he modified the computer to mimic as much of her personality as he could piece together, creating a surrogate Bernice Summerfield to be his companion in solitude. Benny realises the truth; House has cared for Traloor for twenty years, and it has fallen in love with him. And now that the real Benny is here, House fears that Traloor will no longer need it -- and it has gone mad with jealousy.

Adrian has had enough, but his makeshift torch is running out and they'll need light to escape the mad House. Traloor directs him to a storage room with more torches, and although Adrian is reluctant to leave Benny alone with him, she assures Adrian that she can take care of herself. Traloor blames himself for this; all he wanted was for Benny to know the real him, and now he fears that she'll hate him. She doesn't -- but she can't and won't stay on Rhinvil with him, and he is still unprepared to go back out into the Universe. Adrian then calls for help, and Traloor responds... but discovers too late that the real Adrian didn't call out at all. Once Benny is alone, House shuts the door and somehow causes the furniture in the room to fly about, attacking her. Traloor directs her to a secret panel which will lead her to the building site, but neither he nor Adrian can understand how the computer has acquired the power of telekinesis. While Adrian heads for the building site, Traloor goes to the mainframe to shut down the homicidal House. House is enraged and heartbroken by this betrayal, when all it ever wanted was for them to be alone together...

Adrian is shocked when Benny emerges from the passage, dripping with blood, but it isn't hers; the walls themselves were bleeding. House lashes out again, claiming to be far more than a mere machine; for twenty years it's looked after Traloor, caring for him and talking him out of his occasional suicide attempts, and over the years it has developed more and more of a personality. It even carved the so-called artefact itself, on Traloor's instructions, to lure Benny here. House tried to drive her away, by frightening her and sending fake phone calls to pair her up with Adrian so Traloor would reject her; but now it can no longer control its jealous rage, or its desire for revenge. Benny angrily points out that she's no rival; she doesn't actually love Traloor, and after today she'll be glad to see the back of him. But she's unaware that Traloor has been listening to all of this from the mainframe control room. Heartbroken, he blames House for destroying his dreams, and vows to take the mainframe apart piece by piece. Rejected, House goes completely mad -- and the cliff itself begins to crumble apart and shower down upon Benny and Adrian. In the mainframe room, as Traloor begins to smash the computer apart, it speaks to him, promising that it can make things right. It can be better than Traloor had ever imagined; he and Benny can be together forever. House still has Benny's voice, a perfect copy now that it has heard the real Benny, and despite himself Traloor gives in to temptation.

Adrian and Benny try to circle around the mansion to get back to their shuttle, but just as they come within sight of the shuttle it explodes. They head for the beach, hoping to hide in the caves from which Adrian's men quarried the rock for the extension. But when they enter the caves, they finally find Adrian's men, or what's left of them; a shrine has been constructed from their body parts, with the artefact placed in its centre. Traloor seems to be standing in the shadows, but before the enraged Adrian can attack, he steps forward to reveal that he is no longer entirely Traloor. House has embedded electronic implants in his body and brain, and they have merged into a single entity, part House and part Traloor, together forever. But as Benny was beginning to suspect, there is even more than that -- the planet itself is a part of them, for Rhinvil is alive. When the extension was added, the mansion finally took on critical mass and was able to take revenge against the brutish thugs who ripped apart the living rocks. Just as they made their dwellings from its substance, it has made a dwelling from theirs.

Benny is enraged; Traloor may be part of a unique life form now, but why celebrate its birth with murder and destruction? As far as it is concerned, however, love is what has brought them all here now. Benny points out that Traloor was not in love with her, but with an ideal image of her. And now his unrequited infatuation, House's jealousy, and the planet's pain and rage have all been mixed up into one mass of conflicting emotions. Benny tries to get through to what remains of the man she first met, but it's of no use; he now hates her for rejecting him, and he intends to kill her and Adrian slowly. But fortunately for Benny, Adrian is of a more practical bent, and while she's been keeping Traloor talking he's planted quarry charges in the cave. He primes them to detonate, and flees with Benny as the Traloor-thing lunges desperately at the charges, trying to defuse them. It's too late, and the charges go off, burying it and the shrine.