It's a big moment in the life of young Martin Moone: his last week of primary school.

It's Martin last week of primary school. And he's pretty chuffed about it. "This is it, Sean Murphy, the last ever Monday morning. A new dawn is rising when boy becomes man." But before Martin can move on, Sean thinks he must leave a mark on the school to ensure no one forgets his legacy. Enter Martin Mayhem. Although in the face of chaos, it appears that Marty may not be a natural anarchist after all.

Meanwhile, Debra and Liam embark on a mission to stop Sinead from finishing the year at the top of her class to avoid sending her on a Girl Guide Jamboree. However, they soon have bigger things to worry about when Fidelma and Dessie, complete with his "Daniel O'Donnell hair and creepy eyes", drop a bombshell.