@D.B. They skipped a chapter or two. If I recall correctly they and back to fight the scorpion king and in the process Chris's arm was smashed and he got the crystals to "revive" her. Since she's dead she can't feel the damage on her body. It's been a while since I read the book, but I'm pretty sure that's what happened. But for Some reason I thought it was just Muir that returned to fight him.
