Robin's sister Katie is coming to visit New York for the first time, and Ted suggests that he and Robin take her to the Empire State Building. When Katie arrives, Robin is surprised to see that she is with her boyfriend Kyle, who is in town visiting his cousin; Kyle is immature, obnoxious and calls both Robin and Lily attractive in front of Katie. Katie tells Robin she is planning on having sex with Kyle, which terrifies Robin. The gang takes Katie to the Empire State Building, which becomes the basis of several metaphors for sex that they use to discourage her from having sex. Katie is annoyed by this and accuses Robin, who lost her virginity aged 16, of being a hypocrite. After Robin tells Katie to wait for the person she loves, Katie asks Robin if she loves Ted, sparking an argument between the couple.