“Parallels” is episode eleven of season seven of Star Trek: The Next Generation.
Worf is in a shuttle, heading back to the Enterprise after winning a bat’leth tournament. But he anticipates a troubling situation when he returns.
Back on board, Riker is talking about problems with the Argus array again. Worf is not entirely paying attention. Riker comments he looks tense. Today is Worf’s birthday and he assumes Riker or one of the others would try to mount an unexpected social gathering. They are at Worf’s quarters and as he enters Riker says he would never do that as he hates surprise parties.
Worf enters his quarters and makes his way through. To have everyone yell ‘Surprise’ at him. Riker returns and puts a hat on Worf. Riker loves surprise parties.
Worf is sung a song in Klingon and a cake is brought out. Worf states that was not a Klingon song; they’d translated “For He’s a Jolly Good Fellow” into Klingon. Riker explains that Captain Picard was needed on the bridge. Data gives Worf a painting; he’s in his Expressionist phase. Troi hangs it on the wall.
Geordi speaks to Worf, who suddenly becomes dizzy. He blames the painting. Then says he thought the cake was chocolate. Troi wishes; she has a gift from Alexander, a cast of Alexander’s forehead. Worf thanks her for watching him whilst Worf was away. Captain Picard is eating cake and asks Worf how old he is. Old enough.
At the Argus array, the array is functioning normally, but the data is being transmitted elsewhere and Data can’t access the main computer. It’s being transmitted to an uninhabited sector, but Worf says there could be a ship or relay station. Riker is going to beam across with a repair team.
Worf finds Troi in Ten Forward. He wants to speak to her about Alexander. Worf tries to be a good father to Alexander and at times feels like Troi is a mother to him. He appreciates this and wants to formalise the arrangement, for her to become his SoH-chim, Alexander’s surrogate mother, so that if anything happened to Worf, she would be responsible for him. The closest analogy is stepsister. Troi considers and says that would make her mother Worf’s stepmother. Worf’s face shows a look of absolute horror. But he decides that’s a risk he’s willing to take.
Then Data asks Worf to come to engineering. Worf. Geordi and Data are explaining to Captain Picard that the array has been reprogrammed to spy on Federation locations related to new starship development. There’s also data on a Cardassian ship approaching the array. Worf comes over dizzy again; when he opens his eyes, Data and Geordi have swapped places and the captain has gone. He heads to sickbay as suggested.
In sickbay, Dr Crusher suggests this is a side effect of the concussion. Worf has no memory of concussion; the doctor says a competitor hit Worf over the head in the bat’leth tournament, which cost him the match. Worf says he won and can prove it. Only his trophy is now for ninth place and his personal log doesn’t match the one from the beginning.
Worf is on the bridge when Data asks for the metallurgical scan. Worf has no memories of being asked. A Cardassian ship approaches and makes inquiries as to why they are so close to the Cardassian border and Cardassian captain wishes them the best of luck with their repairs of the array, which he is sure would never be used to spy on a neighbouring species. Afterward, Worf says that was the ship that reprogrammed the array; it matches the one from the sensor logs. No-one else knows of such logs. Captain Picard wants the array re-examined.
Worf is speaking to Troi about his different memories when Geordi enters. There’s no Cardassian ship in the array’s logs, nor any evidence it was reprogrammed. It was a simple mechanical failure. Worf is dizzy again and suddenly Data’s painting is hung on a different wall. Then it changes completely. As have Troi’s hair and clothing.
Worf feels faint and he’s suddenly on the bridge. A different bridge. The Cardassian ship is attacking and Worf doesn’t know how to raise shields as the console layout is different. Riker takes over but the Enterprise has to flee, damaged. and the Cardassians destroy the array.
Worf initially thinks he’s suffering from memory loss, as Dr Crusher stated, but the differences are too great for that to be the explanation. Some of the differences are significant. Like being married.