"A Change of Heart," by Raymond Goree, in Alfred Hitchcock's Mystery Magazine, October 2012.
I'm not on the committee that decides on who gets the Robert L. Fish Award for best first mystery of the year, but they're crazy if they don't give this one a careful look.
The narrator is a Las Vegas cop who, at around age 40, suffers a heart attack. Turns out his ticker is in horrible shape. ("Like trying to sew Jell-o together," says the surgeon.) After some more horrible luck ("Jokes on you, says God.") he gets a heart transplant. By coincidence he had met the donor, a cancer patient named Sammy, in the hospital.
After the operation he feels obliged to go to Sammy's favorite restaurant once a month and order the man's favorite, very unhealthy, sandwich.
Sometimes Sammy joins him. Not to eat, of course, just to watch him eat. Creepy, huh?
But wait, there's more. One month Sammy tells our hero that his daughter has gotten involved with would-be bank robbers. "I cant get through to her," he complains. "It's like I'm not even there."
So Sammy wants our hero to stop the robbery and save his daughter. "You
owe me," he insists. But will a robbery really take place? And if it does, how can the cop explain what he knows?
Wonderfully written, one-of-a-kind plot. Highly recommended.