Ever since TOS Season 2 and Mirror, Mirror, the Trek writers have known they can always score big with an alternate universe.
This time, Harry Kim (for reasons too complicated to explain here) winds up back at Starfleet HQ in San Francisco. He never made it to Voyager (and, as a result, neither did Tom Paris, which makes sense) and instead he’s back with his sexy yet impossibly bad actress girlfriend. He’s a respected engineer and his apartment has a view of the Transamerica Tower. Why on earth would he fight to get back to the Delta Quadrant?
Because that’s his destiny, dammit!
Chase ensues. Good shit.