Butterflies (1978)

Season 3: Episode 6

Whilst the boys build a fallout shelter - which annoys Ben when he falls in the hole - Ria meets up with an old friend, Kathleen, an American on her third marriage, and she is no more faithful to this husband than the others. She is amazed that Ria and Leonard have not had sex and asks Ria to pretend to her husband Tony that they have been together whilst she is with her lover. Tony turns up and catches Ria off guard - she is hesitant, and when Kathleen returns, she argues with her, unaware that Adam is listening. He finds out about Leonard but is happy to keep his mother's secret, and when Leonard rings, he answers and hands the phone to Ria.