Rachel's pregnancy has her hormones running wild, and she tries to find some action. Ross and Mona get photos back from their date at Rockefeller Center, and Mona wants to send one out together as a holiday card. Ross agrees but is actually freaked out, and he's forced to consider where the relationship is going. In an effort to prove he's ready for the next step, he gives Mona a key to his apartment. Later he has second thoughts and gets the lock changed. Because Monica doesn't like Chandler's recently divorced Boss, Chandler tries to cancel a dinner date with him. His boss gets suspicious, so Chandler says he's cancelling because he and Monica broke up. But it back-fires when his boss insists on taking him out to some strip clubs. When Rachel explains her sexual frustrations to Joey, it occurs to them that they could get together for the night. But that would just be too weird.
Rachel: You gave her a key to your apartment?
Ross: Not just a key. I gave her the only key. I am now a homeless person in a very serious relationship.