The Bliss of Mrs Blossom (1968)

Harriet Blossom is married to Robert Blossom a businessman whod rather spend the night at his bra factory than at home with her One day Harriets sewing machine breaks so Robert sends a repairman Ambrose to fix it Its lust at first sight for Harriet who convinces Ambrose to hide out in the attic for a tryst When her new beau shows no desire to leave the pair begin a yearslong love affair right under Roberts nose