DC Duncan Lennox is on a week's secondment to Scotland Yard's Art and Antiques Squad. Investigating a young woman, Tessa Gannon, who tried to sell a forged painting to a gallery, Lennox finds a receipt from a gallery owned by an art dealer named Ivor Gregory, who has form for deception. Lennox befriends an artist named Richard Townes, who charges into Gregory's gallery as Lennox peruses the paintings. In the hope of getting a closer look at one of the paintings, Lennox arranges for his wife Shona to buy one of them. He gets it verfied, and is disappointed when it is an original. Shona insists on keeping it, but sends it back to the gallery to be re-framed. When the painting is returned, Lennox realises Gregory has swapped it for a fake, and it's the work of Richard Townes, but to his horror, Shona returns the painting to Gregory before the squad can arrest him. Tessa Gannon admits she had a painting copied by Townes, but she too is in possession of a fake. Gregory is arrested, and Lenn