While attending a college reunion, Pam is taken hostage by Jerry's former roommate who's now a professor. He demands that the school stop their atomic production program or he'll detonate one of his own at the school's field-house during that night's big basketball game.
A vicious counterfeiter escapes from prison and hides out in a remote cabin while recuperating from plastic surgery he received to alter his appearance. His gang lures the Norths to the cabin and holds them hostage, their plan being to ultimately kill the couple.
The Norths travel to Mexico City to help their friend, Det. Paco of the Mexico City police, solve a missing persons case. As they board their plane for the flight back to the US, they don't know that someone has planted a bomb aboard the aircraft, and it's ticking away.
Amelia Little, someone Pam hasn't seen since childhood, comes for a visit. Pam believes her odd behavior is simply a case of being overwhelmed by the big city. The truth is she's an impostor who tossed Amelia off the train and assumed her identity. She's actually Violet Budge, a killer on the run for murdering a wealthy old woman. Pam's in danger of become her next victim after determining the supposed friend is actually a phony.
Gordon Lane, a suicidal invalid, is bitter about his life and jealous of his wife's lover. Marion Lane feels trapped in an unhappy marriage and wants her lover, Barry, to kill her bed-ridden husband. When Barry turns up dead in the Lane's home, Marion is the only logical suspect But when the Norths visit, Pam discovers the truth behind Gordon's disabilities and finds her own life in jeopardy.