The Cryptic Killer

Their lives were in his hands. He has forty-eight hours to brek the code. The clock is ticking. Two murders, each one discovered forty-eight hours after New York City Homicide Detective, Jack Head received a mysterious coded letter he failed to decipher. When he received the third letter, the pattern was clear... he had forty-eight hours to crack the cipher, or there would be a third victim on his conscience.
Time was running out. But Jack would soon learn that his growing list of murder victims would be the least of his problems.