As the formula for a lucrative drug developed for Grisha consumption falls into the hands of those who would abuse its power, hunters rally around both the Brotherhood and the Templars, picking off any Grisha they can get, selling them off to the highest bidder. Captured after the mission in Lisbon, Shay Cormac- a young yet powerful Heartrender- finds himself dragged back into the war he had hoped to leave after being purchased by the Templars. Running out of options to recover the formula before it finds its way into the public's hands, Haytham Kenway, an illusive Shadow Summoner, feels he's left no other choice than to take the drug himself. The Assassins-using Liam's curious knowledge of the drug- feel they are closer than ever to shutting the Templars down and claiming the formula, to keep it safe and out of malicious hands.
Feeling a storm brewing, Shay steels himself for encounters with those he would've rather stayed in his past, the race to the formula bringing both groups Grisha the brink of destruction.