Plot hole: The Thorwalds were supposed to be in the apartment for only six months according to the lease, their phone number wouldn't have been published in the phone book for such a short lease.
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Plot hole: Helena is ordered to fly or be thrown off the tower, bearing the brunt for Simon's failure. But the flying apparatus is still up there, and so is her servant who was going to secretly operate it so that Simon could pretend to fly around. All she needs is right there in front of her. She's supposed to be cunning and resourceful, and she could have saved her life simply by following the original plan.