Revisiting
Okay, so I re-watched the last scene of Dead Clade Walking.
I may ramble here, but hey, that's the only me you get.
So, my new theory (which probably should have been obvious, but I'm a little thick), is that the skull that Sherlock's been fooling around with is essentially a stand-in for his own. (Duh, right?) So, since he really can't exorcise his own demons directly, he's giving it a whack by using a proxy.
Only....as he is coming to realize....you cannot achieve healing by proxy. It has to be direct, or nothing. One has to take one's own medicine.
Recall that earlier in the ep, Randy discusses his ex, and how she's a horrible influence on him, and he knows it - and Sherlock empathizes, bringing up his own relationship woes - but when asked directly whether he 'cut her out of his life', as was his recommendation for Randy, he evaded the question.
Drilling into the skull is his attempt to 'exorcise' his demons in the form of his new addiction - his inability to let Jamie go. His thoughts are unhealthy, and must be 'drained'. He knows it, but is trying to circumvent addressing things directly - *not* 'drilling into his own skull'.
So, he's about to go to work on the mounted skull one final time, and just as he's about to get started, Joan distracts him with the dinosaur remains. He eagerly digs into them, forgetting not only the drill and skull, but also starting to tune Joan out. This dino was a *survivor*, he says, and its remains deserve respect. (There's a little bit of ....something then, between Joan and Sherlock - he starts getting vague on her when she asks him whether he feels good (about solving the case) - and it's like he had to be dragged back to that idea, like he'd been *completely* out of that space, and almost thought it odd that she'd think he *should* be there - and she says she 'knows what he's thinking', which seems to prompt a 'thank you' from him, and him giving her credit due. He then gets playful about offering to extract the evil humors from HER skull, which she almost seems to sweetly consider, before turning him down. And he pauses for a moment, watching her go, before turning back to opening his box (which he never does get to open). I'm not quite sure what to make of that little interlude, so, any help would be appreciated.
Before Sherlock can open the box, there's a knock at the door - it's Randy. As they enter the living room, Sherlock gives a quiet, regretful glance towards the mounted skull (which has carefully been in-frame the whole time) - he knows he won't be returning to finish his self-appointed task. He also knows why Randy's here (and it has more to do with that skull that first glance would indicate. The blocking is interesting here - Sherlock is positioned directly between the skull and Randy, not fully turned toward either of them. Sherlock is dealing with the same situation, balanced on both sides of this equation.). Randy has gotten high with his ex. Sherlock seems resigned to this information, totally unsurprised. But Randy has also kicked the girl out, and told her to never return. (I don't think it's an accident that her name is Eve - the 'first woman', and lifegiver, juxtaposed against Sherlock's 'the woman'.)
As Randy explains that he's cut Eve out of his life, Sherlock is glancing toward the skull, and nodding - he understands that this is the right answer, the right thing to do. (He could read this as a failure of his sponsorship, HIS failure, but then also a way to rectify and repair that sponsorship.) He appears to be agreeing with Randy, but suddenly, the whole scene has become not about Randy at all, but all about Sherlock, and he is not unaware of that fact. Sherlock interrupts Randy with 'do you want to go to a meeting?'
But - though it looks like Sherlock is just being a good sponsor, taking his sponsee under his wing (and he is), in truth, this meeting is more for Sherlock. In that instant, he more deeply understood his own personal addiction, to maintaining connection with Jamie, which can only lead him down a dark, dangerous path, and he knew that *he* is the one who needs help, who needs to sit in a meeting and admit that he's an addict. His sponsee, in 'failure', was still able to have the fortitude to change course and do the right, harsh, necessary thing. Sherlock is at a similar crossroads, and now he is more fully aware.