The story gets under way at a weekend house party where a scientist is murdered and his secret papers stolen. Putting his "little grey cells" in action, Belgian detective Hercule Poirot methodically pieces together the clues, revealing the culprit to be -- you guessed it -- the Least Likely Suspect.
Mathilde Strangerson, the daughter of an eminent scientist, narrowly escapes being murdered in her own bedroom by an unknown assailant. As the room was locked from the inside, no one can understand how the attacker managed to enter or leave the room. Reporter and amateur sleuth Joseph Rouletabille arrives on the scene to protect Mathilde and resolve the mystery of the yellow room.
This film follows Jean, a young French soldier who is physically and mentally scarred by his experiences on the front lines. He struggles to readjust to civilian life, and his family soon realizes the extent of his trauma. Jean's childhood sweetheart, Madeleine, is now married to his friend and fellow soldier, Pierre. Jean's family fears he will succumb to his despair, and they desperately search for ways to help him find peace.