Almost enough to make you forget that they had, after all, given him up for dead.
Something I've been wrestling with -- wrapping your silver lining in a nice dark cloud so you can bring about a happy ending as neatly and with as much under-handed subtley as you can.
"Frodo was alive but taken by the enemy" does it as elegantly as any story I've ever read. Gandalf's reappearance, OTOH, brings only some troubled minutes while Aragorn, Gimli, and Legolas try to figure out who it is and whether to trust him. (And let's not get into Bill the pony. True, you can get away with far more in the denouement.)
In Have His Carcass, Dorothy L. Sayers had the mysterious grandson, who had gone off to Ireland -- suddenly appear and be utterly willing to talk and explain why his grandfather had been so mysterious about where he was and what they had been up to, off the shore where the murder took place. Lots of good evidence -- but Sayers had set Harriet and Lord Peter up with a good supply of theories that the evidence utterly overthrew. So the general effect is: we have to start all over again from scratch because of him.
In Komarr, OTOH, I thought that Tien's death was convenient. It brought a whole bushel of problems, but even when it happened, it was clearly freeing Ekaterin.
I'm still wrestling.