Conundrum (Star Trek: The Next Generation)

"Conundrum" is the 14th episode of the fifth season of the American science fiction television series Star Trek: The Next Generation, and the 114th episode overall. It aired in syndication starting February 10, 1992.

In this episode, the entire crew suffers complete memory loss after an unknown alien ship scans the Enterprise. Although unable to recall their names or duties, they quickly realize that somehow they still know how to operate the starship. With their memories limited, no one notices that Kieran MacDuff, identified by the ship's computer as the Enterprise's executive officer, is someone they've never seen before. The computer also provides evidence that they are on a mission to cross into Lysian space and destroy that species' central command, as well as any Lysian vessel that attempts to stop them. Somehow, it all seems wrong to Picard, but his new first officer insists he must follow his orders.

The episode won an Emmy Award for Outstanding Special Visual Effects.