Isabella suspects her cat Midnight is a vampire after she mysteriously appears at Isabella's gymnastics class despite the doors being locked. Isabella conducts an experiment leaving Midnight locked in the basement but finds her in her bedroom in the morning, believing this proves Midnight is a vampire. Isabella spies on Midnight and notices behaviors like biting mice on the neck and turning into a bat that further convince her Midnight is a vampire. Hoping to protect others, Isabella hides garlic in Midnight's fur, believing this will prevent her from harming people as garlic wards off vampires.