So they visited a spacehulk that forced their ship out of the warp(just like that they where in a collision course). Anyway, one of the human ships where pre-crusade design so they decided to investigate and download eventuall information(the Rogue Trader got annoyed wtih the Explorator for being so adamant about it and stayed behind). Well there one of their crew got infected during a blackout(the ships powersource was on low effect and had its geller field flickering).

In the end they did not quarantine anyone so now the genestealers spread througout the ship.

Any ideas on how to continue with this?

well, if they were merely stung by the ovipositor, how did the genestealers infest the rest of the ship? 'Stealer victims usually go home, and start breeding up a nice population of hybrids. A few generations later, the Tyranids follow the signal.

If they know that there are genestealers on board now, then they're going to have to geld everybody.

Well with stealers i would say that they decided to slip on board the players ship (much easier to deal with a previous existing genestealer cult than building a new one) then inform your players that children are being born on the ship at a alarming rate (throw in like a 56% increase in mutation rates and birth rates) then let them try to track down the sources (i assume you didn't tell them about the infestation) then have crew members dissapear as they are brought under the sway of the mangus and the brood father, the only problem is that genestealers work very slowly to infest a population, might just be easier to just have lots of crew members get bloodly massacred in the halls, and the one or two that survive have little to no recollection of the events that transpired, oh and they test positive for some mutation in thier genetic code....DUH DUH DAAAAAAAAAH!!!

Anonymus said:

One genestealer can infect and destroy a world.

If your players did not understand this, I would make it clear and maybe allow some retroactive fixes out of mercy.

If they already did understand this, but did nothing anyway, then I would have the genestealer infestation start killing the crew in large numbers. Make it significant. A large portion of the ship's crew hurt, the rest demoralized, and some ship's components damaged or destroyed

If the player's rally everyone and scour the ship from stem to stern, I'd let them win (and also get a break from the normal mutant activity in the bilges) so that the campaign could continue.

If the players do anything less, they've shot themselves in the head (possibly a second time). Maybe a second explanation from the GM is in order? Maybe a TPK and a new campaign?

RainOfSteel said:

Sounds like a perfect opportunity to explore another area of the ship: The Archives! A great chance for Seneschals/Explorators to shine as they research what the hell is going on and find increasingly disturbing clues. And sabotaged data crypts...

i would agree with Plasmafest, if they don't understand genestealers they really need to otherwise bad things happen..

Dark Bunny Lord said:

In this type of situation, the GM could rule that in a ship full of thousands or tens of thousands of crew, perhaps one has seen duty in the Imperial Guards against some genestealers and can scream out, "Oh no, genestealers, we're all going to die," before becoming hysterical and collapsing.