Sweet Polly Purebred calls on Underdog to remind him that it's his birthday, and that she plans to give him a party. Meanwhile, the curator in London wishes to loan the famous Excalibur Sword Collection to the San Francisco Museum. Fearing that someone will steal try to steal it, they send a message to Underdog for his assistance to guard the collection. While en route via train, Riff Raff and his gang attempt to steal the sword collection by derailing the train. When the train wrecks, Underdog engages Riff in a duel with the sword collection that was scattered from the wreck. Riff and the gang flee and Underdog attempts to put the train back on the track but seems to be in pain from his back. An ambulance is rushed to the site.
