Watch The Mechanic
In the beginning a plane lands at a hanger with only one passenger. This passenger walks to his mansion with an armed escort. While he goes swimming in his pool he finds a watch at the bottom of the pool. There he picks it up but is grabbed by a stranger and kept there until he drowns to death. This murder was done by an assassin named Arthur Bishop. He escapes the mansion and gets away through a river. After this assassination attempt is done, Bishop is paid by Harry McKenna in Columbia. There they discuss Harry's son and leave.
Over the course of the film, Bishop is ordered to assassinate Harry and is told by a man named Dean that a failed mission in South Africa resulted in Bishop's agency members being killed. Bishop and his protégé Steve go around looking to assassinate a man named Burke and another man named Andrew Vaughn.