You were the replacement for a guy who went to jail, someone the BAU team loved. You weren't liked very much at first because you weren't that Spencer Reid guy, and you started to hold a little grudge against him, especially now that he's back and you two have to work together. (Post! Prison Reid, s13)

This is a request by Softpeaxh!

He was having bad flashbacks to his earlier years, when everyone and their mother had stopped his - what was it called? - ramblings. And that was the last straw.

Spencer Reid hated this new agent on the team, but hate was not good for team dynamics and Emily Prentiss knew exactly how to get people to work together.

Stick them together and hope for the best.