Marta Blackwell (Nicky Guadagni) is a hidden villainess from Werewolf Skin, the 60th book from the Goosebumps series, as well as the two part episode of the Goosebumps TV series (airdate November 22, 1997).
Part 1[]
Marta and her husband, Colin Blackwell, live in Wolf Creek, where their nephew, Alex (the main protagonist), moves in with them. However, Marta is also a villainess prowling around Wolf Creek as a werewolf, as she and Colin often went to an abandoned house and put on their werewolf skins, allowing them to prowl around Wolf Creek as villainous werewolves under the full moon. Throughout Part 1, Marta hid her sinister secret and acted as a sweet-natured aunt to Alex, while warning him not to go out alone at night. Later that night, Marta turned heel and put on her werewolf guise for another night on the prowl with Colin. In the end of Part 1, the evil Marta attempted to attack Alex, as she and Colin made attempts to reach through the bars on Alex's window.
Part 2[]
The werewolves were scared off by Alex in the beginning of Part 2. and after Alex told his aunt and uncle about his encounter, Marta inserts the idea in Alex's head that the Martlings, their eccentric next door neighbors, are the werewolves, stating that they attacked Hannah Stoneman's brother some time ago. However, Alex went out looking to take photos of the actual werewolves, and while doing so, he discovers a shocking truth, that Marta and Colin were the werewolves.
Marta was revealed as a villainess when Alex spotted her and Colin going into the abandoned house (that they claimed the non-existent Martlings lived) and removed their werewolf skins. Knowing that his aunt and uncle are under the spell of the pelts, Alex and Hannah took the skins and buried them. However, with the full moon closing in, Marta appeared with Colin and begged Alex to give them their pelts, which came to life and attempted to attack Alex. Once the full moon appeared in its entirety, the skins were destroyed, and Marta and Colin were free from their curse.