The show has perhaps the most memorable opening sequence of any Star Trek episode. The ship has suffered heavy damage and attempts to control the disaster are failing. Captain Picard issues the frantic order "All hands abandon ship. Repeat, all hands abandon..." as the ship explodes.
After the commerical break, the episode resumes as if nothing happened. Riker, Crusher, Worf, and Data are playing cards, but a sense of déjà vu allows Dr. Crusher to call Riker's bluff. Crusher then goes to sickbay to treat Geordi LaForge for diziness, and again thinks she's done the same before. After she goes to bed, she is haunted by strage voices.
Soon after, the Enterprise loses power as a second ship emerges on a collision course with it. Riker suggests decompressing the main shuttle bay, but Picard takes Data's advice to use a tractor beam. This fails and the ship is again destroyed like it was in the opening sequence.
The same scenes are repeated again after the commercial break, but the crew experiences a greater sense of déjà vu. They determine that they are caught in a time loop. They work to figure out a way to escape the loop for the remainder of the episode.