Ripley sets Ash's head up on the table and plugs him back in, hoping he'll know how to kill the alien.
Ash tells the crew that they can't kill the creature, because it's the perfect organism: hostile, remorseless, with a survival instinct free of "delusions of morality" (Alien). In other words, basically a Wall Street stockbroker. Now we really are scared.
Ash tells the crew it won't lie to them about their chances, but mockingly offers them its sympathies.
Ripley unplugs Ash and lays down the new plan: They'll take their chances in the shuttle and blow the ship up. Parker is on-board with that idea.
Before they leave, Parker sends Ash his regards by way of flamethrower.