I'm reasonably sure this is post The Gift but not definite. I think Spike was fetching Buffy back from heaven and had to keep fighting his way as heaven tried to reject his presence there as an evil demon. I'm not sure, but I think he is placed in there by PtB or some oracles or some such and has to travel crossing some mountains and then eventually finds Buffy at the house in Revello. Joyce is there and he has to persuade Buffy to leave with him by choice. I think he tries to pretend to threaten Dawn, implying he might start a sexual relationship with her or something like that to try and make Buffy care what is happening and want to come back. In the end Buffy agrees and is in a room with tPtB and fights/argues for Spike to get to be returned too as he wasn't supposed to make it, she may have even seen a playback of him agreeing to sacrifice himself.
There may have been some weird mind thing with Willow having to use some magic mind threads and breaking down a door to get Spike access to heaven in the first place rather than other powers, really uncertain.
I know that is all quite vague but a bit unusual so hopefully it will ring bells. | 
