Assassin - Knight Takes Queen

What is an assassin to do when he is forced to take a contract he does not want to fulfill? If he happens to be the best assassin in the galaxy, he fulfills the contract, exactly and to the letter. If that target is a well-loved leader, revered by billions, it must make no difference. A contract is a contract.
How many will live and how many must die, and will "Quantum Magic" play any part in it?