An Upper East Side man was dealt a double dose of cruel fate. First, he learned his toddler had been diagnosed with a serious disease. Then, hours later, bat-wielding thugs beat him in an unprovoked attack, authorities said.

The saga of Jae Kim, 41, began Thursday, when he first learned that his 3-year-old child was suffering from a serious ailment, one that police could not identify.

The distraught father went to nearby Carl Schurz Park at 86th Street and East End Avenue later that night to think and deal with his heartache, investigators said.

He told police he was then attacked by four men, one carrying a baseball bat. Kim staggered back to his building, where a doorman called 911. No attempt was made to rob Kim. He was treated at New York Presbyterian Hospital and released.