Chased one out of the attic about 20 minutes ago, and found where he was getting in. There is a spot where they are able to lift the soffit vent and climb in. Good thing I watched him leave, otherwise I never would have found that.
Bad news is it's going to be really, really tough to get at. I can't reach it from the attic. I can get at it from the outside, but I'll have to use a ladder... I hate heights.
Worse yet is that I think it's my fault, I had torn the covers off in September to properly vent the soffits, and I must not have fastened them back on well enough. And I rented 3 lifts of staging to do that work... maybe I'll get my neighbor to go up there with a ladder.