I think the real Spike, might never left the basement, and the Spike we see helping the scoobies could be another entity (Morphy or princeipal wood) .
we never see Spike leave or enter . he just seems to pop up and that disappears. When ever Buffy ask for his help, he truns her down, only to pop up later.

In "Help" Buffy went to
see if Spike would help her, but he declined. Yet, he showed up later o help, and left before she could say anything.

The guys had set a
trap so anyone coming in will be hit by a arrow, yet the trap didn't
go off until Buffy tried to leave. If Spike had left, it would set
off the trap, . I know that Spike was already in the school's
basement, but the door that had the trap on it ,was the door leading to the " library "
my question is "how did Spike enter the *library without setting off the trap?

also,
In same time,same place ,did anyone else notice the pics on the wall going up the stairs in Buffy's house?
what are they of? They look like all doors!

*Note:Buffy,Cassie and the guys where already in the library.