Mona & Walter & Sam & Eric Who's the Boss? : Season 6 Episode 16

Sam and her boyfriend Eric want to attend a concert. But Eric usually spends the evenings with his (widowed) grandfather. So Tony gets an idea: Mona should instead spend the evening with him. But then when it turns out that Eric's grandfather is the man, who Mona let down 40 years ago at the wedding, the general feeling is at zero level.