I assume that if the demon who holds the deed to the crossroads deal dies, the deal is broken, ownership of the soul reverts to the person who made the bargain. Sam kept trying to find and kill the demon who held Dean's contract.

Sam assumed that, but I don't think it's accurate. There's probably, like, demonic probate courts and codicils to the contract like, "Kill me, Dean Winchester, and Bobby Singer never gets the clear title to his soul."

Oh I'm sure Crowley's made sure his ass is covered. Sterling never loses, after all.

See, now I'm picturing a crossover where Sam and Dean hire Team Leverage and things kick off with Nate saying, "Let's go steal a soul."

Because that would be awesome.

if you're talking about Crowley dying by a mortal's hand, then you're right. That's how attempts to break crossroads deals usually go, by killing the demon who holds the contract.

That's what I meant. If a human killing Crowley voided the deal, taking the soul by contract (as opposed to taking it and hiding it somewhere) wouldn't be any insurance at all.

Sam assumed that, but I don't think it's accurate.

Show didn't do anything to contradict that--didn't the demons he tried to kill to void it just tell him that they didn't hold the contract?

I'm willing to accept the idea that Bobby still has his soul and Crowley just has the title, but it's messy writing, including the unchallenged assumption that killing him would actually fix everything. I mean, Sam still thinks that, no? I don't have the episode to hand, so I can't say exactly what Crowley said when explained his insurance policy.

See, now I'm picturing a crossover where Sam and Dean hire Team Leverage and things kick off with Nate saying, "Let's go steal a soul."

Want!

I did bump into a Leverage/SPN crossover where Sterling was possessed by Crowley, but sadly it was really badly written. I liked the conceit, though.

Ooh, I love that conceit. Not worth reading if it was poorly done, but maybe it'll lead to another, better, story.

Canadian Actor Bongo does lead to some interesting dilemmas in crossovers.

I vaguely recall someone promising that both Dean and Sam would end up safely in Heaven after the big showdown, so if that can be trusted saying yes to possession by Lucifer might not mean anything negative for Sam's soul (given he's doing it for noble reasons). Assuming that Michael wins and he gets vaporized along with Lucifer, anyway.

It just occurred to me that even if their plan to re-cage Lucifer somehow succeeds, it's not necessarily all wrapped up in a bow. Michael still wants the big predestined confrontation too, and would still be in charge of the heavenly forces and free to start everything rolling toward that same conclusion all over again.

saying yes to possession by Lucifer might not mean anything negative for Sam's soul (given he's doing it for noble reasons)

It does seem to be the equivalent of a soldier throwing himself on top of a grenade to save the guys around him, doesn't it?

As for the Michael issue, unless they (Team Free Will, that is) still have one of the angel-killing knives and can use it on whatever vessel is housing Michael, then you're right. He'll still be out there making plans. At which point I guess it's up to the God of this particular universe to finally make an appearance and take a stand.

So you think Michael would free Lucifer or work against caging him just so he can have the big fight?

The angels did have to take mostly a back seat and let demons and humans set him free the first time--what would it take to get him out again?