Summary: Will is upset when he finds out that, despite what she says, Grace is still dating Nathan. He is further hurt when Nathan moves in with them after his ex walks in on him and Grace at his apartment (which, it turns out, is really hers).

Meanwhile, in the ongoing search for his dad, Jack writes a letter to the 11 Black boys, one of whom his mother says is his father. Jack is thrilled when he recieves a reply from Joe, one of the Black boys, but is utterly disappointed when Joe's wife arrives with the sad news that Jack's father died 5 years ago. So Will and Nathan decide to cheer Jack up by toasting to Joe with alcohol. They end up bonding and collapsing on the bed together.

Will's disappointment returns when Joe and Larry have to cancel on their planned scuba trip. Grace is also in a bad mood when Karen hints that, as Grace's relationship with Nathan heats up, her relationship with Will will change for the worse.

That night while at the movies, Grace and Nathan are sitting together, with Will sitting further away due to lack of seats. Grace panics when she thinks Nathan is going to tell her he loves her, and she goes back and forth between the two men, hoping to get Will's help. Will doesn't see why Grace is so worried, and Grace returns to Nathan, but by then, he's dropped the subject and is watching the movie.

Meanwhile, over at Grace's office, Jack is going through different stages of his adjustment to not having a father. As he and Karen discuss the situation, a young boy enters and asks for Karen. When Karen identifies herself, he asks if she knows Jack. When Jack identifies himself, the boy introduces himself as Elliot. He asks Jack if he made a donation at the New York sperm bank 13 years ago. Jack admits that he did, and the boy continues, telling Jack that his mother was nurse there and wanted a baby, so she took Jack's sperm and...he's Jack's biological son.

At the cafe, Grace surprises Will with tickets to Maraco to make up for his missing the scuba trip. Will asks if Nathan's going, but she brushes it off, and Will thinks no more of it.

Back at the office, Karen tricks Jack into talking to Elliot. Jack at first denies Elliot's parentage, then says he doesn't want a son. Elliot says he just wanted to meet him and hits home with Jack when he mentions how hard it is not knowing your father. Jack tells Elliot that he never knew his father either. Elliot asks if maybe he and Jack could hang out a bit sometime, and just as he's leaving, Jack asks Elliot if he wants to go get a burger.

Back at Will and Grace's, he and Grace prepare to go to the airport . As Will's packing, Nathan enters and Will finds out that Grace broke up with him. Will is shocked and tries to figure out why she dumped Nathan. As he's leaving, Nathan mentions to Will that he loves Grace.

Will arrives at the airport in a limo and immediately asks Grace about Nathan. Grace replies that she's worried that if she and Nathan become close, her relationship with Will will change. Will assures her that if it did change, it would only be in a good way. He then tells her she can either get in the limo and go back to Nathan, or fly away to Maraco.

Grace takes the first choice and finds Nathan waiting in the limo for her. Meanwhile, Will runs into his "imaginary boyfriend", a man he's been interested in for a while but has yet to talk to. The man says he, too, has been interested in Will and tells him that he's flying to Paris. Will decides to change his plans and join him.

Quotes
NATHAN (to WILL, who's reading a book in the nude): "Careful, that's a nasty paper cut waiting to happen."