In a hallway, House limps into Wilsensei. Wilsensei speculates that Elizabeth Mitchell is allergic to God. Several cancer patients check out of the hospital for unrelated reasons.
House and the Martins limpeconference as House tells them they forgot to check inside Elizabeth Mitchell for an allergen, so he orders a full-body scan, like, I'm sure that couldn't have been taken care of at some point before Elizabeth Mitchell decided that death was better than this hospital.
Later, the Martins discover something on the scan. I'm no expert at deciphering religious imagery, but it seems like something divine may have been spotted in Elizabeth Mitchell's feminine parts. I doubt House will need any further convincing.
But actually, House informs us that it's a "copper cross," which is a form of birth control pulled from the market in the '80s. Apparently, when Elizabeth Mitchell had her abortion, the IUD got stuck somewhere and has remained undetected until now, and the copper is the allergen. One might wonder how Elizabeth Mitchell just plumb forgot about the piece of copper stuck up into her nether regions. Perhaps she took that whole "our lives begin when we take out vows" crap a little too seriously. Chase says that all they have to do is remove the IUD and the symptoms should disappear...
...and in the clean room, he's telling Elizabeth Mitchell just that. If Elizabeth Mitchell is uncomfortable discussing the foreign object that's been festering in her reproductive organs for over twenty years with the former seminary school student, she does a good job of hiding it. Chase adds that you can be exposed to an allergen for years and only have minimal symptoms, but one last exposure -- in this case washing the new copper cookware and subsequently eating food prepared in it -- can be enough to set off a full-blown reaction. Elizabeth Mitchell asks Chase if he'd like to hear her favorite Biblical passage. Chase nods his assent, and Elizabeth Mitchell recites, "Celebrate and be glad, because your brother was dead and is alive again," which Chase recognized as the parable of The Prodigal Son. That's pretty saccharine for a favorite passage, if you ask me, but it is a Christmas episode, so I shouldn't be surprised to be getting an anvil in my stocking. Elizabeth Mitchell tells Chase that God will be waiting for him when he's ready. He replies that they're scheduling her surgery for the next day. Sure, no rush.