Although Simon practices safe sex all the time, he immediately panics when his girlfriend of the moment, Sandra (guest-star Olivia Allen) confesses to him that she has an STD the next morning after they had sex together. Meanwhile, Martin and Mac (guest-star Kyle Searles) catch Ruthie's boyfriend, Vincent (guest-star Thomas Dekker) on a date with another girl and try to figure out a way to tell her the bad news to Ruthie. Also, Matt, Lucy, Kevin and Ruthie have second thoughts about telling Eric and Annie that Mary is not pregnant again, but in fact has decided to desert her husband Carlos (guest-star Carlos Ponce) and her baby son Charles and is getting a divorce. Lastly, Annie decides to go to New York to pay Mary a visit, but doesn't yet know about the whole situation.