The squad want to give Garrus a lap dance from asari dancers. When he refuse, it turns out that Grundal and Erash had made a bet with Mierin on whether Garrus has a secret wife/husband or not.
"You've had - girlfriends before? Or the turian equivalent? Please tell me your first experience with sex isn't going to be with a ghost. Because that would be the saddest thing I've ever heard."
Zel'Aenik nar Helash had gone on Pilgrimage, and decided to go crazy at the end instead of home. At some point, she became a viral specialist and decided "serial killer" was what she wanted to be when she grew up.
The Shadow Broker's files in Mass Effect 2 reveal that Zel was killed with a cough, but what wasn't recorded is that it was a complete accident on Garrus's part. The guy was sick for days and was planning to just put a bullet into the quarian's head but accidentally coughed on her instead. After that, you know the rest...