Salem, the cat from Sabrina the Teenage Witch,is in possesion of a magical time ball, and has somehow stumbled upon John Adams High.
After Mr. Feeny finishes a lecture on World War II, Topanga shows Cory a picture of her grand parents, who got engaged on Pearl Harbor day. She tells him they were Cory and Topanga's age, and Cory wonders what it was like at that time.
Upon hearing this, Salem transports everybody back to the 1940's. Cory tells Topanga he's glad the US hasn't entered the war, "I could never be away from my best gal." As soon as Topanga returns the sentiment, Mr. Feeny enters and grimly informs them that the US has, in fact, entered the war. "May God be with us all." Shawn appears and encourgaes Cory to enlist with him.
Back at the Matthews', Alan and Cory are preparing to ship out the next day. Eric, a torture risk due to his ticklishness, is not going. Topanga drops by to ask Cory if he wants to see Glenn Miller, but when Cory breaks the news, she gets upset and runs out.
There's a goodbye party for the soldiers at Chubbies. Topanga's not there, however, and Cory's worried. She finally appears as the men are boarding the busses. Cory proposes, and she happily accepts.
In a fox hole, Cory is reading a letter from Topanga when a firefight begins. Before they head out, Cory tells Shawn to marry Topanga if he doesn't make it. Shawn has reservations, but he agrees.
When it's announced over the radio that the war is over, Cory runs out of the trench. "The cease-fire will commence in twenty-four hours," continues the announcement. Shawn runs after Cory, but there's an explosion.
At home, everyone is upset because Cory is still missing. Shawn proposes to Topanga, telling her it was Cory's last wish. She agree's but no one is happy. Amy, certain Cory is alive, sends Eric to Europe to find him.
In Paris, Cory is with a girl named Versailles. He's lost his memory and become "Pierre, the tortured French-speaking artist." He paints an unknown girl from his dreams.
Eric and Jack enter, looking for Cory. When Jack points him out, Eric tackles Cory in a big hug. Cory has no memory of his brother, however, and refuses to go home. He asks Versailles to marry him.
Meanwhile, Topanga can't marry Shawn, and she rushes out.
Cory and Versailles are about to get married when Topanga bursts into the cafe, still in her wedding gown. Versailles recognizes her from Cory's painting. Cory still doesn't remember, until a scolding from Topanga reverses his amnesia and they kiss.