The Fordyces of High Wycombe are giving a buffet party. Among the guests are their neighbours Jean and Frank Morris. The guests discover, to their horror, that they are meant to be the buffet for two cat-sized spiders.
Two days later, the TARDIS materialises in High Wycombe. The Doctor doesn't want to stay, but Romana wants to explore. She bets him five Gallifreyan pounds that they can find something unusual. K9 detects a dangerous animal presence and then shuts down. The Doctor and Romana encounter a pizza boy who is delivering to the Fordyce home. He tells them of strange nightmares among the people and noises in the drains. They offer to take the pizzas to the Fordyce house and send him on his way with a bag of gold.
The Doctor knocks on the door and Mr Fordyce answers. His resonses to the Doctor's questions lead them to think he either has a mental implant or is under hypnotic control. They split up to sneak into the house. Meanwhile, an alien intelligence in the house stirs, detecting an enemy presence.
The Doctor sneaks in through the bathroom and finds Jean. He lightly hypnotises her, as she is terrified of something. He enters the living room and sees the Fordyces, and watches as two spiders jump off their backs and voraciously eat the pizzas. They are called away by their leader, and the Doctor rejoins Romana outside, where K9 has also joined them. The Doctor explains who the spiders are, remembering them from his previous encounter.
The Doctor heads upstairs in the house, after giving K9 instructions to destroy the house if he doesn't return in fifteen minutes. Romana, left alone, is captured by the spiders, hypnotised, and brought to the Queen Spider upstairs. The Doctor, meanwhile, has made his way upstairs and tied two of the Queen Spider's legs together while she slept. The Doctor is captured, and Romana is freed from hypnosis. The Queen Spider gloats to them about her plans to lay her eggs. Just then, K9 begins his destruction of the house. The captured humans and the Fordyces run from the house. The Doctor and Romana make it out as well, but the Queen Spider stops the house from burning by blowing on the fire.
Fire trucks arrive, and the Doctor orders them to flood the house. This kills the Queen Spider and her eggs. The Doctor gives her two spider minions a second chance and agrees to take them to the planet Arachnos. The Doctor claims to have won the bet because things like this always happen to them, and therefore it wasn't unusual.
- Fourth Doctor
- Romana II
- K9 Mark II
- Jean Morris
- Frank Morris
- Mrs Fordyce
- Patrick Fordyce
- Queen Spider
- When trying to identify the alien presence, the Doctor considers, and rejects, Daleks, Cybermen, and Zygons as possibilities.
- The story mistakenly calls Frank Morris "Patrick" at one point; Patrick is Mr Fordyce's name.