Something causes the TARDIS to act irrationally; the ship takes over its controls and travels to the source of the problem: a jumble sale in a church hall on present-day Earth. The Fourth Doctor and Sarah investigate the various stalls, searching their wares for anything unusual. While Sarah buys an assortment of bargains, the Doctor finds a stall called the ‘Curio Imaginarium’ run by a conman named Travis Lunquist, who shows him a rare crystalline sphere he allegedly discovered in China. The Doctor recognises the object as a Xanthene node, but is out-bid by another bargain-hunter called Brock…