I'm at the Chasing Echoes quest on the side of the Dawnguard, but Serana won't let me continue until I get rid of my follower. The problem is, I told my follower to wait somewhere and I can't remember where. Is there any way to find out where I left my follower? Thanks.

Some folllowers if you have wait to long will return to the place you recruited them.

Do you know what follower you currently have?

Which platform are you on, and which follower did you have?

PC and I can't remember. It's been a while since I've played the game.

If you could remember the follower's name (and ID), you could teleport them to you or vica-versa. http://www.uesp.net/wiki/Skyrim:Console

Wait for 36 72 hours. The follower will leave your service.

*Vice versa.

That's what I get for speed-typing. Thanks.