Apothecary. Rygel groans and starts to sit up behind Zhaan.
Cargo bay. Rygel gasps, "That frelling thing went through my mouth. Could barely frelling breathe!" He says it built the cocoon around him to keep him as a meal for its offspring. Crichton shoves his blaster against Rygel and asks, "How do I know you're Rygel?" Cue the squeaky flatulence. Rygel whimpers at a higher pitch. Crichton wordlessly looks at Aeryn, and they both start running. With his helium-altered voice, Rygel calls, "Where are you gooooing?"
Another race down the corridor. Aeryn tells Zhaan to get out of the apothecary. Crichton adds, "It's not Rygel, it's the parasite!" Zhaan turns just in time to see the fake Rygel launch itself at her, knocking her down. Chiana wakes up as Zhaan screams. The fake Rygel's face starts to sort of...bubble...as Crichton and Aeryn arrive. Crichton pulls Rygel off Zhaan and tosses him across the room, toward D'Argo and Chiana. Chiana says, "Rygel?" and then takes in the sight of Aeryn and Crichton aiming guns in her direction. She falls on top of D'Argo as they open fire. Rygel takes a couple of direct hits, and bits of his head seem to disintegrate. Then he suddenly collapses into nothing. Just like Obi-Wan did. Only shorter. And grosser, since a second later a kajillion little bugs skitter out from under Rygel's cloak. Er. I guess that's a spare. Okay. The bugs race toward Crichton, Aeryn, and Zhaan. Crichton tosses Aeryn his gun and moves to grab something. Aeryn starts shooting as Crichton pulls a hose out of the wall. I think it's a fire extinguisher. Let's just assume so, to simplify things. He starts spraying the floor while Aeryn keeps firing. After a minute, they stop, and the clouds of vapor slowly fade away to reveal that the floor is now carpeted with frozen, dead bugs. Aeryn crunches one under her boot in a satisfying way. From her perch on D'Argo's sickbed, Chiana asks, "What the frell is that?" Aeryn and Crichton look at her and chorus, "Sorry about the mess." They give each other a "Jinx!" look, and march away before Zhaan can demand they help sweep up the bugs. If I was Chiana, I would be staying on that bed for quite a while. Ew.
Some time later, Rygel is wrapped in a blanket as he explains that the parasite was in a crate he was "inspecting." He says, "It was actually feeding off my essence, my thoughts." The bugs certainly aren't discriminating diners. D'Argo says that he remembers the other Rygel standing over him after he was attacked by the Vorc. Chiana wonders why the parasite didn't imitate D'Argo. Zhaan says, "I suspect it tried, but D'Argo's reaction to the venom was so strong, it didn't have enough time to complete its task." Rygel asks how they possibly could have been taken in by the imitation, and D'Argo says it was a perfect copy of him. Rygel sniffs, "Perhaps to undiscerning observers like yourselves. Fortunately, that courageous Vorc was here to rescue me!" Well, that answers all of the questions. Except, of course, how Zhaan was able to come up with an antidote when all of the bugs were killed.