I'm running a cinematic one shot (2-3 sessions) starting tonight based on Hope's Last Day.  I'm using Hope's Last Hand (an act that was created for before HLD) as a first act.  HLD will be second and final act.   All this is just before the marines show up in Aliens movie.

Spoilers for Hope's Last Day ahead





FIRST
In HLH, an infected prospector was brought back to the colony LV-426.  It's all hush hush, but word gets out that some kind of serpent has bitten people and it escaped into the colony housing.  Everyone's ordered to lock down.  The PC's, upset with how Weyland-Yutani have been treating them, have been plotting for weeks to rob the casino.  The lockdown is their chance to get over there unnoticed.  Of course mayhem will just start.  PCs will get glimpses of something very wrong as the Xenos begin to form a hive as they start to kill.

I want this casino heist to then turn into HLD for Act II.  Ideally, the group is away for half a day to a day so that I can show the build up of people concerned to all hell's broken loose.

HLD is designed to be run as one act on its own.  Story as written: PCs went to fix a processor off base.  Their vehicle broke down and they trek back to the colony building and discover they are in the thick of Xenomorph take over.  Their only chance is to steal a keycard from an offworld inspection team and take their shuttle to escape.

As HLH is ending, how do I get the PCs out of the base . . . . but then compel them to come back so I can run HLD?

I'm not sure being sent on a maintenance run is plausible enough.  Any suggestions?

Maybe they learn that there is something or someone that might help them in their heist back at the base.  Someone has info on the schematics of the place or knows where a much more lucrative stash is.  Not sure I'm reading this all right, but that was what came to mind.  I've noticed that most people on here mainly play old D&D games, so you might not get much help here.