Piper and Paige fight thorn demons in an alley; the female of the species spits thorns and one of the thorns hits Piper. Leo is unable to heal her because he is to face the Elders' judgment, as told to him by Odin and Sandra: he is to be made human and his memories erased. This is a test of whether he belongs with the Elders, or with Piper.
Leo finds himself stranded and alone in rural Texas. A pickup almost hits him and flips over; he pulls the driver out before the truck explodes. He cannot heal, but his medical training proves useful. He remembers his experience on Guadalcanal.
Back to the Halliwell manor, the three sisters demand to know what happened to Leo. One of the elders came down to bring the news and this angered Piper and call her to leave. When the three sisters, depressed thinking about love and giving up love, Drake steps in, cheer them up and encourage them to not give up on love. Which also encouraged the sisters to find Leo.
Leo goes to the local sheriff, who promises to find out who he is. The paramedics had thought his job of patching up the driver was professional. He has a flashback of facing a demon.
Piper, after calling Darryl, passes out. She finds herself out of her body and faced with none other than Cole Turner. The other sisters find Piper, but they are unwilling to call for the Elders. Drake checks the Book of Shadows.
Cole tells Piper that she is trapped in the Cosmic Void and he is here to help keep her and Leo together. Piper is skeptical, given Cole's past.
Leo is in a diner, when the waitress notes the tan line where his wedding ring once was. He has a brief memory of putting a ring on Piper's hand. Outside the diner, he finds a trucker going to San Francisco and asks for a ride.
Paige and Phoebe are in the police station with Darryl. An officer tells him that a John Doe of matching description saved a man's life in Texas. Paige and Phoebe orb to the diner and inquire after Leo. They learn he is heading west.
Cole tells Piper that he doesn't want Phoebe to give up on love. This is why he wants Piper and Leo together. He is cursed to live unloved and doesn't want Phoebe to share that fate.
The truck driver talks to Leo about having a "calling" to work for the greater good, trying to convince him that he should take this path. Paige and Phoebe catch up with Leo, but the truck driver, who they recognize as Odin (though not by name), orbs him away. In that moment, Piper revives, but only Leo can heal her soul. Paige and Phoebe orb to the top of the Golden Gate Bridge and call for the Elders, and Leo and Odin answer. Leo doesn't remember the sisters. Piper, dying, calls to Leo, who hears and jumps from the bridge -- falling from grace. Paige orbs him and Phoebe home, to find Wyatt has healed Piper.
This is Drake's last day of life. At Magic School, Phoebe thanks him for helping her move on; she has found her first real love since Cole. They share one last kiss before Drake walks away and closes the doors behind him for he doesn't want Phoebe to see his death. We learn at the end that the whole thing was set up by Cole, from Drake meeting the sorcerer to the thorn demons. Drake has no regret of anything, from him becoming human to falling in love with Phoebe. He dies and his soul goes to heaven, leaving Cole to walk on Earth.
The next morning, Leo rejoices being human again with Piper.