While searching through historical records, Eric Russell discovers a startling revelation, concerning his own family line. Exactly one century ago, in the year 1978, Russell's ancestor, Philip, as the costumed criminal, the Viper, battled the Flash. An event that would seem to be impossible, as Philip's obituary had been posted that morning. Stranger still, Philip's wedding, to Cynthia Ross, occurred that evening. As luck would have it, Russell's daughter, Picture News reporter, Iris West, was visiting from the 20th Century, with her husband, who happens to be the Flash.
Russell proposes a visit to West's era, with his wife, Fran. The Flash agrees, and draws West and the Russells back to the 20th Century. En route, Russell thinks back to the day he sent his infant daughter, West, back in time, to save her from nuclear annihilation, to be raised by Professor Ira West. The time traveling party arrives to find burglars in the house. The Flash quickly grabs the thieves in his slipstream, and runs them over to police headquarters. West takes her mother on a shopping spree. The Flash, as police forensic scientist, Barry Allen, makes plans to spend the day with his father-in-law.
Russell, though, has other plans. While Allen is gathering more era-appropriate garments for his father-in-law, Russell teleports to San Francisco. Activating his uniform's invisibility aura, Russel begins his investigation into his ancestor's strange past. Moving at super-human speed, Allen, as the Flash, attunes his vibratory energy to the same frequency as Russell's teleporter, tracking him to San Francisco. Russell visits the morgue, only to find that Philip's body has disappeared. Russell's investigation carries him to Philip's office, where he works as a private investigator.
Philip's last casebook entry strongly suggests he murdered his arch-nemesis, the Viper. Arriving in San Francisco, the Flash is drawn to a robbery in progress, perpetrated by the Viper. The Flash confronts the Viper, easily dodging his opening attack. To protect the innocent bystanders behind him, the Flash uses a slab of sidewalk to block the Viper's acidic blast. The Viper switches tactics, attempting to gas the Flash. The Flash windmills the toxic vapors back at the Viper. The Viper feigns distress, in order to get close enough to expose the Flash to his paralytic toxin.
Russell discovers the Viper's journals in Philip's office, along with a large sum of stolen money and gems. Russell confirms that Philip is the Viper. His ancestor suffers from a split personality. References in the casebook to destroying the Viper indicate that Philip thought he had suppressed his Viper identity forever. The Viper side of his personality, however, willed Philip into a deathlike coma, allowing the Viper personality to become dominant. The man that walked out of the morgue was not Philip Russell. It was the Viper. The Viper drops the paralyzed body of the Flash off a cliff, and into the ocean.
The Flash shakes off the paralysis. Moving at super-human speed, the Flash generates a waterspout, that he rides back up the cliff face. Seconds later, the Flash has beaten the Viper into unconsciousness. Russell arrives, and fills the Flash in on his findings. Using 20th century materials, the Flash helps Russell cobble together a "Psycho-Healer". Russell uses the device to remove the Viper personality from Philip. The Flash returns all of the Viper's ill-gotton gains, leaving Philip to keep his appointment at the church. The Flash rushes Russell home, arriving just ahead of West, and her mother.