DOCTOR WHO IN DETAIL

The TARDIS materialises in the grounds of a small manor house. The presence of a vintage car suggests Earth around the 1920s. In the library a man - Professor Peach - is killed by lead piping - and a giant wasp.

The Doctor uses his psychic paper to invite himself and Donna to the party that is happening at the house. The Doctor talks to Lady Eddison and learns about the Unicorn - a noted jewel thief. More guests arrive as the Doctor and Donna watch. Lady Eddison introduces a special guest - Agatha Christie.

The Doctor picks up a newspaper and notes the date: the date Agatha Christie disappeared. No-one knows why, but her car will be found by the lake, and ten days later she appears at a hotel with no memory of events.

Professor Peach is found, and a broken watch on his wrist reveals the time of death: 16:15. The Doctor uses his psychic paper to set himself up as Chief Inspector Smith, and he orders people downstairs for an interview. The Doctor finds morphic residue, meaning someone is an alien in human form.

The Doctor starts talking to all the people assembled in the drawing room. Everyone says where they were at 16:15. No-one has an alibi. Whilst the Doctor and Agatha talk it over she shows him a piece of paper taken from a fire. All that can be read is 'maiden'.

Upstairs Donna is looking for clues, and she finds a locked room. The butler unlocks the room. The room has been unused for 40 years. Dona hears a humming at the window, and opens curtains to reveal a giant wasp. It smashes through a window. Donna uses a magnifying glass to direct rays on to the wasp, allowing her time to escape. Outside the room she meets the Doctor and Agatha. The sting from the wasp is sticking through the door.

In the kitchens the staff are gossiping about the murder. The head housekeeper realises the truth and goes to warn Lady Eddison, where a gargoyle falls from a roof onto her. The Doctor hears this and rushes outside. The Doctor, Donna and Agatha see the giant wasp and start chasing it before it changes back to human form. When the Doctor shouts several rooms open as everyone appears.

Donna and Agatha are talking outside, when Agatha notices a neat garden bed has flowers that are bent. Looking closer she finds a locked box. She takes it to the Doctor, and when he opens it he finds a lock picking kit - signs the Unicorn may be around.

The Doctor feels something is wrong. His drink has been poisoned by sparkling cyanide. He rushes to the kitchen for ginger been, walnuts, anchovies and a shock, the latter provided by Donna kissing him. This enables the Doctor to reverse the effects of the cyanide.

Later on all the guests are taking dinner. The poison gives the Doctor an idea. He laces the soup with pepper. The active ingredient is piperine, an insecticide. A storm breaks outside, and gust of wind opens the windows and blows out the candles, and they can all hear a wasp.

The wasp appears and the Doctor grabs a sword. Lady Eddison's necklace has been stolen, and her son has been murdered. The Doctor calls together the remaining guests, and calls upon Agatha to take over the investigation. Agatha suspects that the real Robina Redmond never left London, and that the Robina Redmond there with them was really the Unicorn. Robina gives herself up as a thief, but not a killer.

Agatha turns her attention to the Firestone necklace Robina stole. This was brought back from India 40 years ago, where Lady Eddison contracted Malaria. In India she had fallen pregnant. But it was no ordinary pregnancy. In India Lady Eddison fell in love with a man called Christopher, an alien Vespiform in human form. On returning Lady Eddison gave her child to an orphanage. Professor Peach had found the birth certificate, and the head housekeeper had been on her way to tell Lady Eddison about this.

The Doctor deduces that Reverend Golightly is really the Vespiform, Lady Eddison's unknown son. The Reverend hadn't realised about this part of himself until a break-in at his church meant his anger revealed his true self. This awakening re-activated the Firestone crystal that Lady Eddison had been wearing, returning his memories, plus what Lady Eddison was thinking about at the time: she was reading an Agatha Christie novel, which is why all the murders appeared the same as those found in the Agatha Christie novels.

Reverend Golightly turns into the wasp. Agatha Christie runs away with the Firestone crystal, and the Vespiform follows her. The Doctor and Donna follow them to a river. The Firestone crystal is thrown into the lake, and the Vespiform follows it. The Vespiform and Agatha are linked and Agatha collapses. Before it dies the Vespiform releases Agatha, and she loses her memory of events.