Prison Break producer, Zack Estrin, has revealed some great series spoilers for season four, due to kick off on Sky One this September.

“We’re going back to some old-school, season one storytelling with the book,” Estrin told website Zap2it.

“Just as Michael’s tattoos [in the] first year, the book has this season’s mysteries in it – riddles, clues, puzzles. Our guys will need to get a hold of that book in order to complete their tasks for season four and… T-Bag is the keeper of that book. How they find him, and what happens when they do, becomes an integral part of the plot.”

Estrin added: “Obviously Whistler was a bit of a mystery in season three, but you will find out exactly what he was up to. His real agenda will be revealed.”