A Fateful Switch

As he is being sedated for emergency heart-by-pass surgery, Sean Kelly, an American business man of Irish descent, briefly starts talking in German. When the Chief surgeon shares this after surgery with the patient's young adult children, they are shocked to hear this and do not know what to make of it.
When Sean Kelly is asked about this, he at first denies that this could have happened but he knows it to be true. He struggles at first but then realizes he has to lift the veil of his secret life for the past thirty years.
In a letter to his son Ryan and daughter Lisa, he explains how he had switched identities with his best friend who was killed while they were serving together in the French Foreign legion. He confesses to have been borne in Germany and his true name is Hans Schumacher.
The story now takes dramatic turns and leads to very unusual discoveries in Germany while resulting in surprised endings.