Star Trek: The Next Generation (1987)

S1E11 The Big Goodbye

Stardate: 41997.7. While engaging in a Dixon Hill adventure on the holodeck, Picard, Dr. Crusher, and Data find themselves in peril as the system experiences a catastrophic malfunction. Trapped in a gritty 1940s setting, they must contend with menacing mobsters while seeking a way to escape the escalating chaos.