Charles tore his attention back to the main engineering compartment, just as the main door crashed inward, revealing a compartment that was strikingly different from its human counterpart.  The modular design he had expected was non-existent; instead, all of the alien subsystems appeared to be linked together into a single unprotected mass.  It made no sense to him; half of the systems appeared to be exposed to any stray shot or power surge.  Or were the aliens in the middle of trying to blow up the ship when the Marines burst in?

“The gas seemed to make them convulse,” Jackson reported, as the Marines slowly advanced into the engineering compartment.  The aliens seemed to have vanished completely, abandoning the section.  “They weren't in any fit state for a fight.  We’ve taken them prisoner.”

The bridge crew, Charles told himself.  “Keep a sharp eye on them,” he ordered, remembering how bendy and flexible alien bodies could be.  Standard zip-ties might not be enough to keep them helpless, not if they could flex their way out of the tie.  “Actually, secure them thoroughly.  We don't know how easily they can escape.”

“Yes, sir,” Jackson said.

The Marines prowled through the deserted compartment, looking for the aliens.  There was so much interference in the section that the nanoprobes, otherwise very useful at tracking alien movements, were largely useless.  Charles heard bursts of interference over the datanet, wondering absently just what the aliens used to operate their starships.  Nothing human produced such effects, of that he was sure.  Or would human fusion cores produce interference, if they were unshielded?  The prospect of fighting in a radiation-filled zone was chilling.  But the battlesuits weren't reading any dangerous radiation in the vicinity.

“It's like they abandoned the entire section,” Corporal Pollock said.

Charles rather doubted it.  There were four compartments on a human starship that had to be held at any cost; the bridge, main engineering, the armoury and life support.  Losing control of one of them could mean losing control of the ship.  The contingency plans the Marines had practiced for Ark Royal included stationing a whole platoon of armoured Marines in all four locations, ready to repel attack or buy time for the ship to be destroyed.  But the aliens seemed to have retreated instead ...

The mists grew heavier as they advanced, making it harder and harder to see.  Charles sensed the tension among his Marines, understanding and cursing it at the same time.  What they couldn't see could hurt them – and the tension would make them fire off a shot at nothing, sooner or later.  And then he saw very definite movement, something twitching ...

“Keep back,” he ordered.  Something was barely visible in the gloom.  “Sergeant ...”

The Sergeant advanced forward, weapon at the ready.  Charles silently cursed the rules that forced him to stay back, then almost jumped as the Sergeant swore out loud.  “Sir,” he said, “they’re dying.”