When Megan becomes ill after swimming in a polluted lake, Chris sets out to investigate the source of the contamination.

When burglars strike the McCullough household, Lassie runs off to sound the alarm.

When Uncle Steve takes Will and Megan gliding, they learn that hanging out with him can be dangerous.

Will, Megan and Lassie play ball at Chris's latest construction site- a field scattered with live artillery shells.