Parallels

Worf comes back from a bat'leth tournament and finds that little things on the Enterprise keep changing: the flavour of his birthday cake, where a picture hangs, what his crewmates remember. Then the changes grow larger. In one reality, his confusion at an unfamiliar station during a Cardassian attack costs Geordi his life. Data discovers that Worf does not belong in this universe: his shuttle passed through a quantum fissure, and he has been jumping between parallel realities ever since. In one he is married to Deanna Troi, in another Riker commands the ship after Picard's death against the Borg. While trying to send Worf home, the ship is attacked, the fissure destabilises, and countless Enterprises from other realities pour into the same space. Worf flies his shuttle back through, surviving an attack by an Enterprise from a Borg-conquered universe, and the fissure seals. Home at last, he invites Deanna to dinner.