Fearing he is lost in a parallel world, the Doctor and Gus take off in the TARDIS. Orbiting Earth, the Doctor sees a magnetic anomaly emanating from near the North Pole has created many parallel worlds. The Doctor and Gus land near the anomaly to find its source is a spaceship. Sneaking into it, they find the Time-Meddler and a party of Ice Warriors led by Autek, who are building a giant sonic cannon.
An advanced, secret and surprisingly well informed military group, SAG 3, is also investigating the anomaly. As the Ice Warriors prepare to drop the Doctor into a pit, SAG 3 attacks the ship, frees the Doctor and forces the Ice Warriors to leave Earth. In his TARDIS, the Doctor pursues the Time-Meddler's TARDIS through space and time. After a chase through the Time Vortex, the Doctor appears beforethe Time-Meddler, who attempts to materialise in the same spot. Having two TARDISes in the same place and time causes an explosion which destroys the Ice Warrior ship and sendsthe Time-Meddler to another dimension.
Having solved the mystery of the parallel worlds, the Doctor and Gus part ways with SAG 3 and go on to their next adventure. After the TARDIS dematerialises, SAG 3 are left to wonder if they should have told the Doctor that Gus was going to die...
The character is depicted as going by the name of "the Time-Meddler," with the assumption that the nickname of "the Monk" was simply a nickname named on his specific disguise in medieval Northumberland. Later usage of the character, however, would elevate "The Monk" into the character's default alias, equivalent to "The Master" or "The Rani", although occasionally with the man himself complaining about others having begun to call him that without his consent.
The Time-Meddler's TARDIS is disguised as a police box like the Doctor's, but why this is is never explained.
The Doctor comments that every time he activates the TARDIS, he's sent sideways in time, implying that perhaps all the Fifth Doctor's comic stories have been set on parallel Earths.