The Apprentice, having been tasked to protect the Sorcerer's Hat from anyone who becomes the Dark One, has faced Zoso and Rumplestiltskin. However, while he managed to fend off Zoso, Rumplestiltskin slips a potion in the Apprentice's tea which turns him into a mouse. Anna, who had visited the Apprentice on Rumplestiltskin's orders to slip him another potion, the antidote, decided not to do so as she thought the potion was some kind of poison. When Anna manages to grab the Dark One's dagger, one of the things she commands him to do is turn the Apprentice into a human again. Later, Ingrid - who has the Sorcerer's Hat - visits the Apprentice looking for a deal.
In exchange for the Hat, Ingrid wants to be able to find the perfect candidate to be apart of the sisterly trio that Ingrid wants to create, one of which includes Elsa. After a while, the Apprentice tells Ingrid that the Sorcerer has found the perfect match, but that the person has not been born yet. However, he does provide a doorway from Arendelle to Earth, which is where Ingrid will reunite with Elsa, who had been trapped in a magic urn by her sister Anna, and where she will meet the perfect match for her plans - Emma Swan. The Apprentice helps Snow White and Prince David transfer the potential darkness from their unborn child into Maleficent's offspring, before banishing it to Earth, along with Ursula and Cruella De Vil, although unintentionally. The Apprentice later consults the Sorcerer about this, who tells the Apprentice that the lives of Emma Swan and Maleficent's daughter are entwined. Eventually, the Apprentice finds Maleficent's daughter, Lilith and explains everything about her origins, her birth mother along with the Enchanted Forest, Storybrooke and the inhabitants, including Snow and David.
In Storybrooke, the Apprentice is confronted by Rumplestiltskin and Captain Hook. Hook restrains the Apprentice, while Rumplestiltskin reveals to the Apprentice that he finally wields the Sorcerer's Hat and is now able to unlock its power, before sucking the Apprentice into the hat and storing him and his power there. When the darkness inside Rumplestiltskin starts killing him, they free the Apprentice from the Hat. The Apprentice manages to remove the darkness from Rumplestiltskin. However, it attacks him and escapes, with Emma eventually absorbing it and becoming the new Dark One. The Apprentice tells Emma's friends and family to seek the Sorcerer: Merlin.
Weakened by the attack from the darkness, the Apprentice is cared for by the Blue Fairy, and gives his wand to Emma's family and friends before he dies. In the Underworld, the Apprentice appears to Henry, and warns him not to use his power as the Author to resurrect Cruella De Vil.
- He is based on the apprentice from the fairytale The Sorcerer's Apprentice.
- The fact that the Apprentice turned into a mouse from Rumplestiltskin's potion is a reference to the Disney film Fantasia, in which their take on The Sorcerer's Apprentice features Mickey Mouse as the Apprentice.
- S4, E04: "The Apprentice"
- S4, E08: "Smash the Mirror" (flashback)
- S4, E10: "Shattered Sight" (flashback)
- S4, E16: "Best Laid Plans" (flashback)
- S4, E19: "Lily" (flashback)
- S4, E21: "Operation Mongoose, Part One"
- S4, E22: "Operation Mongoose, Part Two"
- S5, E01: "The Dark Swan"
- S5, E07: "Nimue" (flashback)
- S5, E10: "Broken Heart" (flashback)
- S5, E15: "The Brothers Jones"