A few weeks after the events of Switch, Kai has returned to his former post and, despite suffering from partial amnesia, is well on his way to getting back into the swing of things. Hal, however, has turned in a letter of resignation and cut off all contact with his former colleagues. Meanwhile, a potent new drug dubbed "DF" has hit the market and both of them start on the case. Working as they are from opposite directions, will they meet in the middle or will Kai's memories of the past year as Hal's partner remain lost forever?