In Another Problem in Paris when study abroad student Marie Ho fails to return from her semester in Paris Kai Cooke is hired by her estranged stepfather, psychiatrist Gordon Grimes, to fly to Paris and hand her a sealed envelope. The PI tracks her through Paris neighborhoods, guided by an old flame French professor, and finds Marie living with her boyfriend and another woman. Meanwhile Kai himself is being tracked. When he delivers the envelope Marie's apparent ménage à trois is violently torn asunder. Kai suspects the Frenchmen who have been following him. And behind them someone closer to home.