Following Kalabar's destruction at the hands of Marnie, Dylan, Sophie, Gwen and Aggie, Kalabar's son, Kal, set to work on his own personal revenge against the Piper-Cromwell family. With one of Aggie's spell books already in his possession as a result of his father's purchasing it from Gort more than 50 years ago, Kal sought to venture to the human realm in order to steal the second one.
On Halloween, Kal assembles a Golem from frogs and names it Alex so that he can play the part of his father and provide Kal with a convincing backstory. Together the two venture to the human realm and crash the Piper-Cromwell Halloween party, claiming to have just moved in down the street and bearing lime-flavored punch for the party. Alex distracts Gwen while Kal persuades Marnie to give him a tour of the house - allowing him to steal the second spell book when Marnie shows him Aggie's room. Shortly thereafter, Kal takes his leave, but asks that Marnie be his date to the Halloween party at the high school, which she accepts. Elsewhere, Alex asks Gwen if she'd like to go to the party as chaperones, which Gwen happily accepts. When Alex takes his leave, a frog is left behind, which is found by Dylan and raises Sophie's suspicions about him.
After the party is over, Alex returns in a frog costume to pick up Gwen, providing her with a costume of her own. The two make their way to the Halloween party, while Sophie is left under Dylan's care. During this time, she deduces that Alex is a Golem working under Kal and she and Dylan make their way to the high school in order to warn Gwen. At the party, Sophie expresses her concerns to Gwen - though Gwen remains skeptic. It isn't until Alex returns with punch that Sophie conjures a fly, tempting Alex with it in order to expose him for the Golem he is. Outraged, Gwen destroys Alex, using a spell to reduce him to the pile of frogs that he began as.