The owner of a stamp shop is murdered when excitedly talking on the phone to a contact about the rare Mauritius Penny that has turned up on a list. Cathy Gale applies for a job in the shop, and she and Steed witness another murder in an auction room.

Steed wants Mrs. Gale to impersonate Hilda Stern, a recently arrested assassin about to be used by the trans-national crime syndicate Intercrime. Things go swimmingly, until the real Hilda Stern breaks out of Holloway and confronts the imposter.

Astonomer Professor Richter believes that the sun's stellar companion, a white dwarf, is returning to the solar system. If it does, that's the end of everything. So why on Earth would anybody want to murder him now?

All the occupants of a rest home, Adelphi Park, are multi-millionaires. And most of them are refusing to see anyone, including Professor Renter who was due to fly to America with Steed to show off his latest invention. His wife is unable or unwilling to help and, curiously, the neighbour, Madden, another millionaire, is missing.

Willis-Sopwoth, a top pharmaceutical firm, is being drained by cheap imitations of its products in foreign markets. The death of a member of staff while investigating the fraud brings Steed and Cathy face to face with a deadly artist and a plot to poison children.

Jockeys and stable hands are being trained in the use of firearms and poisons, so Steed delves deep in the murky world of horse racing.

Soviet-British trade talks are coinciding with the first London concert of the brilliant young pianist, Stefan Veliko. A young girl accuses Veliko of assault, and is then murdered. If someone wants to disrupt the talks by incriminating the pianist, they seem to be going about it in the right way.

Has the late Dr Marlow's proposed radar-jamming system been tested against British defences? If so, the dead scientist seems to be doing it from his grave. And what's the connection with the local hospital's bizarre operations and a train-crazy philanthropist?