At a luxurious vacation house on the Canadian coast, a curious house party has gathered. Its object is not sociability but security. The safety of the party is of utmost importance as the attendees are English engineers whose mission it is to design the missile controls for Canada’s revitalized navy. But a mysterious death has already taken place. Could it be suspicious? Who would commit a murder at a party? The amiable MI5 agents, Patrick and Ingrid, who are also husband and wife, are ordered to join the engineers. A gripping game of high-stakes charades is played and all guests take part, whether willing or not. But when an “accidental” car crash is followed by an “accidental” poisoning, Patrick and Ingrid know a traitor is present. Who has crashed the festivities? Will the couple figure out the mystery before the death count rises uncontrollably?