Mr. Burns gets sick and only a transfusion of Bart's blood can save him. After, Mr. Burns is more alive than ever and writes a thank-you note to Bart. Homer is convinced that Burns isn't greatful enough and writes a nasty letter. Realizing it's a mistake, Homer tries to stop Burns from getting it, but can't. After reading it, Mr. Burns vows to ruin Homer's life. However, after a talk with Smithers, Burns realizes he's wrong and buys the Simpsons a gift.