The Blue Heelers are stumped as to who is stealing mail from the neighbourhood letterboxes, so they try patrolling the streets on bikes. Jack seems to be settling in happily with Letty and her baby son—until an old flame of hers turns up and Jack doesn't know where he stands. Tom and PJ head off for a fishing weekend—leaving Tess in charge for the first time. All seems to be going smoothly until some prisoners prove they are a violent, unruly group which takes Tess to the edge. The bashing of one of the inmates uncovers a web of deceit and proves a vital clue to the identity of a murderer.