When Sandy forgets his and Kirsten's 20th wedding anniversary, he finds himself going to a lot of trouble to make it up to her with the help of Seth and Ryan. Lindsay and Ryan grapple with their new relationship: Is Lindsay Ryan's step-aunt or his girlfriend? Meanwhile, Summer meets Zach's family and it does not go so well. In the end it's an anniversary to remember as Sandy surprises Kirsten with a serenade at the Bait Shop. But Marissa ends up alone as D.J. leaves Newport Beach.