Stupidity: Cassie leaves the girls with Ben Parker because Ezekiel would "never find them there." However, the minute Mary's water breaks they all pile into the car to go to the hospital, which makes it hilariously easy for the hacker to find them. The girls were safe at Ben's home because Ezekiel didn't know about it, not because Ben could physically protect them in any way. There's also no reason to go to the hospital in the first place; Ben is a paramedic and can deliver the baby himself.
Stupidity: In the subway, Ezekiel Sims is able to hide from Cassie, the girls, and the police officers, and begins picking them off one by one from underneath the platform. Instead of killing any of the girls, which is his only goal, he decides to kill the policemen instead, allowing the girls plenty of time to run away from him and escape.
Stupidity: After stealing the taxi, Cassandra removes the license plate, and yet the taxi's identification number is located in bold plain sight on the doors and roof light.
Stupidity: The incident, where the three girls first encounter Ezekiel Sims and Cassie saves them, makes the paper less than three hours later, including their photos. So he can call the cops and report locating them.
