New head teacher Karen Fisher is clearly in her element at Waterloo Road and is joined at the school by her husband, Charlie, who is starting as a supply teacher. However, when 15-year-old Harry finds a suspicious message on Charlie's mobile about a lunchtime assignation, he begins to suspect his dad is having an affair. Harry dials the number on the text and is shocked to hear new Spanish teacher Cesca answer. He desperately enlists Sambuca's help and they follow Charlie on his lunchtime rendezvous. Together they spy on Charlie with Cesca, taking a photo as evidence. When Harry later tells Karen she refuses to believe him and assures him that it must be innocent.