You remember when disappeared, right? [You know, the last time she was heartbroken.] He came back from...
From being in love with someone else. They weren't together exactly. They didn't meet in person until he was trying to save her from a stalker. He watched her die.
The geneticist. [Not really important that she's a geneticist, but Reid mentioned it and it had stuck in her mind as she tried to picture the woman. The one he loved more than her without even holding her hand.]