You're Somebody Else

in which he is faced with the love of his life, but she isn't who she says she is.

or

Spencer Reid heads to Boston with the rest of the BAU for a serial rape/murder case involving nine women. While on the case he is confronted with his long-lost childhood best friend, who is living under a different name. This event leads to a spiral of encounters over the next ten years who shape the very essence of who they are.

*also available on Tumblr (same username)*