ridley, standing guard, hears the alarm. he hears chris jiggling the knob. but he sees no door. the walls around him seem to be solid slabs.
ridley is spooked by the sound. frightened, trembling, he un-slings his rifle.
ridley spots a blue access slot in the wall. he levels his automatic and chews the thing up with a short burst.
chris hears the clattering of the troopers heading his way. what he doesn't hear is.  a slight crackling.  in the walls.
chris checks ridley. no pulse. his own rustling movements prevent him from hearing.  that soft crackling sound.
the vines continue to advance.
the troopers trickle into the kitchen to find.  rebecca, kneeling over ridley's corpse, examining the ragged bite on its neck.