 Aunts Hilda and Zelda are planning to go away for the weekend, and, thinking she will have the whole house to herself, Sabrina sees this as a perfect opportunity to throw a party and invite all her friends. All plans go south when Sabrina is appointed a babysitter. Determined to have her party and prove her popularity to all her friends, and nemesis Cassandra, Sabrina attempts to cast a spell on her babysitter to turn her into a teenager. As usual, the spell misfires and she accidentally turns her babysitter into a baby. Sabrina must now find a way to change her back and cover up this mishap before her friends arrive!