1x24 "The One Where Rachel Finds Out"

Ross has to go to China for a fossil dig before Rachel's birthday. Chandler tells Ross to find another girl and get over Rachel. Ross tells Chandler to give Rachel his present, and then leaves. Joey's new girlfriend, Melanie (Corinne Bohrer) wants to go to bed with him, but Joey's participation in a fertility study is preventing this. During Rachel's birthday party, Chandler accidentally lets it slip that Ross is in love with her, and a big decision presents itself.