Mary's feelings for Robbie resurface when she inadvertently finds out he has a secret date for Valentine's Day, and the whole family schemes to uncover the mystery woman. Meanwhile, with the exception of Lucy who has a date with Jeremy, the other Camden kids feel deflated when their Valentine's plans fall through and they end up stuck at home celebrating Sam and David's second birthday. Lucy and Jeremy's first date does not go as expected as they both keep on running into Lucy's ex-boyfriends. Although all's well that ends well by the end of the episode for everyone.

After finding a Perseid floating in a life pod the crew attempts to rescue and give medical aid to him. He returns this good gesture by forcing a pain-full beam of energy into Harpers neck. When Harpers knowledge increases ten-fold and a bounty hunter shows up to take Harper. The crew realizes that the Perseid may have done more than just attack Harper.

John's former flame, Megan (Jaclyn Smith), appears unexpectedly at his door and announces that she has left her husband and wants to move in with John.

Ally has hallucinations with Barry Manilow. Richard assigns Ling to work with Jackson Duper, the firm's newest lawyer. When they meet, Ling discovers that Jackson slept with her in the past under a fake name. They have to handle a double case of a man who wants his marriage annulled because his wife is a nymphomaniac and cheated on him 106 times and is suing the minister for having a torrid affair with her. Between the unisex bathroom, Elaine's vibra and Melanie's Tourette, Jackson is going crazy with his new job and questions his future in the firm. Meanwhile, John proposes to Melanie. But Melanie doesn't want to be institutionalized (even if that institution is marriage)...

It is a bad day at the beach. A man has lost his Rolex watch and is upset when all Sean offers to do is fill out a report-not investigate everyone at the beach. Mr. Tanaka is in the water, trying to learn how to swim properly. Being the rich and old man that he is, he is impatient with the other people at the beach and is completely unaware of the dangers of being in the water. Kekoa is keeping an eye on him. Suddenly, a loose catamaran starts careening towards him. Everyone shouts at Mr. Tanaka to get out of the way, but he feels that he is an important man who does not need to move. Sensing the danger brewing, fourteen year old Kala'i pulls Mr. Tanaka under the surface of the water. The catamaran glides over them, narrowly missing them. Sean, in a daring move, leaps on the catamaran and with the help of Kekoa is able to stop it. Mr. Tanaka, though, keeps accusing Kala'i of attempting to mug him. He refuses to listen to anyone who tells him otherwise.

Doug is surprised to find his married best friend, Deacon, out with another woman. Meanwhile, Carrie questions her relationship with Doug because of their different views on cheating.

Tonight, David Grohl from the Foo Fighters.

Janice Taylor becomes emotionally involved with a young patient when he demands more than medical help after his mother dies. Victoria Merrick jumps to conclusions when she treats a young teenage girl with amnesia and bruising.