Goodnight Sweetheart Season 3 Episode 9

When Phoebe is ill with pneumonia Gary brings her penicillin, the bottles belonging to Yvonne and Ron, who had some for his poorly dog Sheba. Phoebe recovers and, seeing the name Sheba on the label, suspects Gary is seeing another woman. He decides to tell her the truth about Yvonne but she has already fallen asleep.