Over the past 50 years, thousands of people disappeared. This July, they're back.
Why it is hard sci-fi
Forty-four hundred missing people from across a fifty-year window are returned to Earth in a single instant. The show commits to one rule. They are returned by a future-human group as part of a course-correction program, and each of them carries a single ability calibrated to drive a specific change. The shows procedural shape is around the federal agency that catalogues, monitors, and sometimes contains them.
Science inside it
Targeted retroactive intervention through a single-event return, a single biochemical substance called promicin that produces a fixed probability of ability or death, and the operational shape of a federal agency built around a population of statistically identifiable subjects. The show is more interested in the policy than the mechanism and that is a deliberate choice.