1x20 "The One with the Evil Orthodontist"

Rachel and Barry start dating again, which is slightly awkward because he's now engaged to Mindy, who wants Rachel to be her maid of honor. But when Rachel finds out that Mindy and Barry had an affair while she was engaged to Barry, the two women decide to call Barry out on it. Meanwhile, Chandler goes nuts when a woman he likes won't return his phone calls. The friends become annoyed after they discover someone is spying on them from the building across the street.