by Richard Lucas
Designed by Patrick Downing
Directed by Kim Mills
Quentin Slim (Corin Redgrave) sits morosely in a fishing hut while Jackson (Valentino Musetti) removes crates behind him; Max Bush (Gary Watson) arrives, worried about Williams. Slim says he's already arrived and been dealt with; he indicates a corpse, lights a cigarette with an oil lamp, then throws it into some straw, hiding the evidence by burning down the hut.
Steed and Cathy examine the corpse at the morgue - Williams was an agent - and find a rare chess piece in his personal effects. Steed goes to inspect the hut, and finds Dr Stannage, the pathologist, (Norman Scace) already there; he says Williams was shot. Stannage leaves and Bush arrives, saying the hut belongs to Captain Slim and Steed's trespassing. Cathy meanwhile goes to The Chess Shop run by Mason (Burt Kwouk), dropping Williams' name when she shows him the piece. Mason says he's been playing chess by correspondence with Williams, and gives her his next move. Steed visits the Captain (Leslie Sands), who claims to know nothing about the fire, or Williams; Bush concurs, but Slim mentions that Mason is coming to dinner that night. Steed's searching the office when Katie Miles (Jennie Linden) enters; the Captain returns and tells Steed that his son - Quentin, Katie's husband - is dead after his boat capsized in a storm. Cathy tries Mason's chess moves and finds they don't work - they must be a cipher; meanwhile, Mason is discovering Williams had already been killed and is concerned about Cathy - Quentin says they must find out who she is, and deal with her!
Captain Slim tells Bush to push the men harder, as both sides of the operation depend on each other... Steed meets Katie at a chess club, where she reveals that Bush knew Williams, Quentin and Bush spot them together. Cathy revisits Mason and gives Mason Steed's address as her own. Bush meanwhile obtains Steed's address from Dr Stannage. Steed has a call confirming Quentin was wanted for smuggling when he disappeared. Bush gives Mason a package of heroin hidden in a lobster, then gives him Steed's address and they realise it's the same as Cathy's. Steed has a date with Katie, while Bush tells Quentin that Steed's a threat. Quentin wants to go to London to warn Katie, but Bush plans to abduct Cathy and have Steed come after her... Cathy has just deciphered the message when Mason arrives and pulls a gun on her.
Steed returns home with Katie, but sends her home when he sees Cathy's notes and the scattered chess pieces. He breaks into Mason's shop and finds the heroin, smelling of lobster. Katie tries to tell the Captain that Quentin was a crook, but he won't listen, and orders her to leave his house. She tries to 'phone Steed anonymously, telling him Quentin's still alive and living in Le Havre, but he sees through the disguise. Cathy meanwhile fights her guard, Jackson, but Mason prevents her escape. Katie and Steed visit the Captain, telling him about Quentin, Bush arrives and is accused of knowing where Quentin is - he pulls a gun, but is disarmed by the Captain. Back at the hut, Quentin orders Mason and Jackson to the boat, and pours kerosene from a lantern on the ground, Cathy loosens her bonds and they fight, but the flames rise... A body is removed from the burnt out hut, and Steed worries for Cathy's safety - the body is Quentin's and a dishevelled Mrs Gale arrives behind it at the morgue; she'd tried to get him out, but failed.
Cathy plans to take a holiday in the Bahamas, so Steed gives her a swimming costume, suggesting she investigate some trouble out there while "pussy footing" along the shores; she tells him firmly "Good bye". Steed looks confused, then 'phones another woman, proposing a Caribbean holiday...