Ok, Genius.

Doctor Spencer Reid, your adorable dork of a best friend, has never been the romantic type, but you two have always had a sweet relationship. What with your shared intellect and IQ, being the two youngest agents recruited to the BAU, and the fact that you're both absolute nerds (plus you could beat him in Go any day). After a close call you had on a difficult case, Spencer's attitude towards you changes, and you notice.