Well, because he has pictures which shows her dead girlfriend Letty (Michelle Rodriguez) alive. And she is now the part of Shaw's furious little army. From its last destination in Tokyo, the Fast 5 the franchisee is now in London.
So, they are all set to destroy the streets there and obviously would come out with flying colours. Director Justin Lin knows what the car freaks demand and he gives them.
What it takes to produce better than each franchisee is more action, more gizmos like wheelers, more mesmerizing locations, more brutality, and it just adds to blend it perfectly.
