Two nemeses become bonded jilted wives after their husbands reveal they have been having an affair with each other since the 1990s and now plan to get married. As Grace and Frankie muddle through ups and downs with their business, romantic relationships and families, they must face some realities of aging.

All is not well for brilliant but boorish Dr. Martin Ellingham as the hit British dramedy returns. To Martin's utter disgust, his medical practice remains under official scrutiny because of his pre-existing blood phobia, and he is forced to attend refresher courses starting with phlebotomy. His wife, Louisa, and aunt Ruth urge him to take this risk to his career seriously, but events conspire against him.