The whole Carver thing is so confusing because just when you think it's one person, that person is completely discarded due to one detail, and then ten episodes later, they come back to the forefront.
There was someone on a Nip/Tuck board who went into a rather long and involved (and, well, feasible) explanation for how Sean was the Carver back during the summer. It's actually dependent on something you mention, Nathan (the time lapse between the anesthetization of Christian and the murder of the girl last night), as one of the key contentions was that Sean laying in bed holding the gun on episode 02:16 (last season's finale) did not occur concurrently with Christian's assault. This person suggested that Sean was "remembering" what he had just done to Christian and that while we thought at the time we were seeing Christian's assault in real time, we were actually seeing an almost immediate flashback.
4) And Doc, you mention the rape, and I'll agree that's a credible motive for Liz, but if Sean is to be believed (I suppose nothing can be taken for granted at this point) there's no physical evidence it took place.
Well, it has been about three months' time (in the television series timeline) since Christian was assaulted, so from a biological standpoint, he has had a rather long time to heal (physically if not spiritually). I don't think Sean was saying that there was no sign of any trauma (I could be wrong) indicating a rape had even occurred so much as the trauma that had occurred at the time of the rape had healed to a point where it should not be bothering Christian in such a physical manner. More of a "making a mountain out of a molehill" explanation from Sean to Christian, if you will. What I got out of it was that even though a physical assault had taken place, Christian's reexperiencing of the pain in his rectal area was akin to PTSD and a somatic hallucination in the vein of amputees who sometimes claim they can still feel pain in their nonexistent limbs.
If Christian does turn out to be the Carver (and I don't think he will), I'll be shocked beyond shocked. Quentin is too obvious (being the new guy and all) for one reason, and Liz became horribly obvious last night for other reasons.
WHAT WE KNOW:
-Has access to paralyzing narcotic drugs
-Resents physical aesthetics as a primary means of identifying beauty
-Has access to paperwork from McNamara/Troy (the business cards)
-Had knowledge of the nature of last night's case despite the case not being leaked to the general public (I think)
-Has a vendetta (apparently) against both Sean and (particularly) Christian
-Was able to change the anesthesia in last night's operation without arousing suspicion
The argument that the Carver has to be a man (which I've never seen here, actually) is unfounded since the key points brought up for this are great physical strength and a penis (both of which are usually associated with the masculine persuasion). However, the Carver's victims have all been caught by surprise, and the Carver is able to administer the paralyzing agent before the victim is able to react and defend themselves. And as for the penis thing, I have two words: Strap-On. Or if that's one word, strap-on dildo.
After all, no DNA evidence had ever been found at any of the assaults.