Dr Keel is asked to help in the search for a man who has picked up a radioactive isotope, not knowing that it will quickly kill him and harm anyone else he comes into contact with. But Marko, fearing that the police want to find him because of his forged passport, has already gone into hiding.

Six agents have died on an escape route through Hungary and Austria. Anderson, a friend of Steed's, has also gone missing. Steed finds his friend but is then accused of being a traitor and taken to a brainwashing unit in Scotland run by the Wringer.

A series of sudden deaths in high finance leads Steed to dabble in shares while Emma investigates the makers of executive paging devices. Are companies being acquired through a simple and subtle form of murder?