S9·E9 The One with Rachel's Phone Number

Joey becomes convinced that Monica is having an affair, after Chandler sneaks back into town without him knowing, in order to have some alone time with his wife. Meanwhile, Rachel and Phoebe have a girls night out, and Rachel gives her phone number to a guy they meet at a bar. Also, Ross and Mike try to hang out together but it doesn't go very well, since they can't find a common interest to talk about.