Although he practices safe sex, Simon panics when his girlfriend of the moment, Sandra (guest-star Olivia Allen), confesses to him that she has an STD. Meanwhile, Martin and Mac (guest-star Kyle Searles) catch Ruthie's boyfriend, Vincent (guest-star Thomas Dekker), on a date with another girl. Also, Matt, Lucy, Kevin and Ruthie have second thoughts about telling Eric and Annie that Mary (Jessica Biel, who does not appear in the episode) is pregnant again, but also to hide the fact that she has deserted her husband Carlos and her baby son Charles. Lastly, Annie decides to go to New York to pay Mary a visit.

After being taunted for wearing second-hand clothes at ""Second Hand Rose"" by Vincent's (guest-star Thomas Dekker) new girlfriend, Margot (guest-star Ashley Benson), a distraught Ruthie runs into the bathroom and finds Martin's girlfriend, Zoe (guest-star Katie Cassidy), recovering from a fainting spell as two girls try to help her. Zoe confides that her family doesn't have enough money for food and makes Ruthie promise not to tell anyone.

However, when Martin breaks up with Zoe because he doesn't like her conceited attitude, Zoe thinks Ruthie has betrayed her confidence. Meanwhile, Kevin unsuccessfully tries to create some alone time with Lucy, but is frustrated with Lucy's obsession over Savannah. Also, Eric and Annie suspect that Sam and David are feigning being sick so they can stay up late and eat sweets. Lastly, Sam is jealous of the attention being given to an ill David.