A small-town Californian teen finds himself in the 1950s after his eccentric scientist friend conducts an experiment that turned a DeLorean into a time machine goes wrong and he must make sure his teenage parents fall in love before he is erased from existence! (Back to the Future)
After an eccentric scientist builds a time machine, a teenager travels back in time and accidentally prevents his parents-to-be from falling in love, putting his own existence at stake. (29 words)
As a character in Looper says: “This time travel crap, just fries your brain like an egg”. And makes a hash out of loglines, too. In my take, the objective goal is implied: he’s got to get his parents-to-be to fall in love or else he’ll never be born in the future. Oh, and he also needs to get back to his future, er, the present. How can you cram all that all in using no more than 40 words Does it have to be all crammed in?
The hook in the concept was strong enough that the movie got made despite the number of studio brains that got fried like an egg.