Does Happiness Grow Up? - S1.E11

William gets tested to see if he can be a sperm donor for Donna, and is shocked to find out that he is infertile. He is plunged into a depression that he can't be a father, but doesn't tell Lindy, who can't work out what is wrong.

As he withdraws more from her, she finds it harder to resist the flirtations of Robert, the French Canadian executive who is wooing her to come to Toronto and take the job he is offering. When she tells William she's been offered the job, he reacts badly. He doesn't want to go to Canada to live.

Eventually Lindy succumbs to Robert's advances and sleeps with him, but immediately feels guilty. She realises she's giving herself a reason to end her relationship and goes home to William, determined to fix things. William tells her about his infertility and challenges her to admit that she doesn't want kids. Lindy can't answer.

She tells Robert that she doesn't think William will be coming with her to Toronto, but she will still take the job.