PCs are asked/hired to go and pick up (if they have a starship) or escort on a liner (if they haven't) four people from a nearby system. Ideally, get them to agree before they have much chance to do any background research.
The world they'll be going to is a Balkanised water world. The four people they're meeting are political dissidents from one of the governments, a theocracy. The starport is in a different country, a bureaucratic obsessed blood pressure inducing place.
Unsurprisingly, the four dissidents don't turn up for the rendezvous. Depending on things, they've either -been put under house arrest -been arrested by the bureaucracy for a minor traffic violation (driving a powerboat without due care and attention) -or something similar.
The governments concerned (make the planet have at least 4 or 5 for fun) should be sufficiently twitchy that, when the PCs do eventually find out where these people have got to, they can't just steam in with guns blazing. 'cause the military are on standby most of the time, and all hell'll break loose. The way my PCs got them out from house arrest on a floating hydroponics plant (remember, its a water world, makes life much more difficult) was to hack into the theocracy's job allocation computer, have all four of them transferred on a Police boat (so as not to attract attention) to a nearby oil rig, and took the boat in transit during an electrical storm (weather conditions on a slowly rotating (40hr day) water world)
Just for comment, we were using a 2300AD/old Traveller(TM) hybrid (2300AD characters, Traveller universe, hybrid gear with a touch of Cyberpunk(TM) for good measure.)