When an alien satellite causes all of Earth’s transmissions suddenly stop, a retired physicist must find a way to bring them back.
Understood, logically at some point other people on Earth either hear signal as well or become aware of the aliens. If they don’t then the main character could just be going mad, only then it’ll have the cliche moment when the audience are told – ‘it was all in his head’ which could be a weak twist.
I suggest you add a hint of irony to the mystery.
What if the physicist is also, unbeknown to him, part alien, and therefore is the only person on Earth that can understand the alien language. He is then perfectly qualified for being the only man on Earth who can stop them and the whole situation becomes imbued with mystery due to his strange connection with the aliens.
Going off of what Nir said and your own comment: When an alien satellite causes all of Earth’s transmissions to stop, a retired physicist who can hear the communication signals the aliens use must decipher them in order to restore communication.
Or something like that, just throwing ideas out there.