 Dennis and Dudley escape from their predicament in the Gym, but at the cost of unwittingly vandalizing the stage equipment. Justine bumps into an old school friend with a baby, Jackie, who is stuck with her mundane life. She is persuaded to go to a forthcoming party, and Justine arranges for Robyn and Julie to baby-sit. Mrs. Monroe confides in Mr. Robson that she feels guilty about her decision not to allow the girls  play - but then the two of them find the smashed equipment, and conclude it was the girls expressing their dissatisfaction at her veto. The girls deny knowledge of the damage, and decide to find out with their own investigation. Dennis gets increasingly nervous as the day progresses. Mr. Hankin s science class in forensics gives Lucy the idea for taking fingerprints. In the Gym, Hammy finds Dennis cleaning the equipment he hid under, and is immediately suspicious. When the other girls turn up, Dennis talks his way out of it. Mr. Hankin is persuaded to look at the crime scene, and finds a footprint in one of the vaulting boxes. In the evening, Robyn and Julie start their babysitting for Jackie, while the young mother and Justine go off to their party. Before the party starts, they go to the wine bar, and notice Martha there, sitting alone. While they say hi, Mr. Robson comes in, very late, and immediately is in her bad books for talking to the girls first. Ignoring her grumpiness, he takes her off... to the school swimming pool, and his spontaneity wins her back... Back at Jackie s house, Robyn and Julie are finding their charge a bit of a handful, disappearing and making a mess while their backs are turned. Justine sees Julie and Robyn to their homes, then walks home alone. On the way, she suddenly hears a cry, and sees a man running off. Another bloke steps forward, clutching his chest, and collapses in pain. The first house she tries is no help, the occupant too afraid to help, so Justine heads off to a phone box. As she waits for the 999 call to respond, there s the sound of approaching footsteps, and the phone box door opens...