A catastrophe at a science research facility opens a crack "to another dimension" and unleashes strange effects on space and time. The effects are felt more than a light year away on the Enterprise, causing brief moments of time to repeat themselves. The Enterprise investigates and finds that the experiments of brilliant (and single-track-minded) Professor Manheim (Rod Loomis) have gone terribly awry. Only he and his wife Jenice (Michelle Phillips) have survived the disaster. Character twist: Jenice was a former flame of Picard's, whom he stood up on their last date in Paris before he shipped out with Starfleet more than 20 years ago.
This is TNG's first time-manipulation episode (and most definitely not its last), and as Trek time episodes go, it's too simple, straightforward, and arbitrary to really grab our fascination. There are a couple of fun time-related gags, such as when Data, Riker, and Picard wait for a turbolift, only to find themselves waiting for it again, while at the same time on it. But the crisis' solution is too simplistic, with no intriguing puzzles for the characters or audience to work through. Basically, they give Data a canister, which he sticks into a hall of mirrors; problem solved. Talk about your tidily boring solutions for dealing with a "doorway to another dimension."
The character storyline is just a tad more interesting, trying to explore a little bit of Picard's youth. Here was a young man afraid of being tied down by a woman and thus sentenced to a life of ordinariness; I suppose some stories are timeless. But I've had it with Troi's annoying counseling sessions. First she confronts Picard on the bridge about the personal feelings she's sensing from him. Later she asks Crusher (not in so many words) how she's handling her jealousy of Jenice. It's time someone told this intrusive Betazoid to keep out of personal matters that don't affect the operation of the crew.