Jonathan Creek: Jack in the Box (1997)

Crusading journalist Maddie Magellan is instrumental in getting a man released from prison after serving nine years for a murder she believes he did not commit. The next day, the victim's widower apparently shoots himself after locking himself in his personal nuclear fall-out shelter. Investigators and engineers insist that no one could have gotten in or out of the shelter after the door was sealed. Yet those closest to the alleged suicide insist that his hands were so crippled with arthritis that he could not have run the bolts on the massive door, let alone pulled the trigger on a gun. Maddie coerces reluctant sleuth Jonathan Creek into investigating the case.