Jimmy encounters Miri in April, 1967 when he journeys to Krypton's past in an attempt to change history. Feigning amnesia but armed with a knowledge of Kryptonian language and science, Jimmy is mistaken for a Kryptonian and assigned a job as "a Science Council page" and housed with Zak-Lor in Kryptonopolis. While working as Zak-Lor's lab assistant, Jimmy meets Miri, a beautiful brunette who works in the mining division of the Submarine Palace, deep beneath Krypton's oceans. The two fall in love but Jimmy is unable to convince Miri or the rest of Krypton of the planet's impending doom.
After a series of near-death experiences during which Jimmy is mistaken for a criminal and mentally controlled by the Phantom Zone-prisoners Jax-Ur and Varox, Jimmy is finally rescued by Miri, only to lose her forever when Krypton is destroyed. As Jimmy saves himself with his time travel device, Miri and her father fall through a crack in the planet's surface. Her last words, which she attributes to Jimmy, are borrowed from Shakespeare: "Parting is such sweet sorrow..." (SPJO No.101: "Olsen's Time-Trip to Save Krypton!").