This makes Vader seem more like a demonic presence, and also serves to prove Obi-Wan a far wiser man. Vader plays right into Ben's hands and thus the Falcon escapes. What is confusing is exactly when someone had the idea to plant a tracking device on the ship. They never found anyone on it, and it was only later that Han, Leia, Luke, and Chewie were fighting on other levels. Only Vader suspected Ben of being on board. He and Tarkin argue over it and suddenly after the Falcon leaves theres suddenly a magical tracking device!!