What did Gene say to Finny before he left the infirmary?

From the text:

“Finny, I’ve got something to tell you. You’re going to hate it, but there’s something I’ve got to tell you.”
“My God, what energy,” he said, falling back against the pillows. “You sound like General MacArthur.”
“I don’t care who I sound like, and you won’t think so when I tell you. This is the worst thing in the world, and I’m sorry and I hate to tell you but I’ve got to tell you.”
But I didn’t tell him. Dr. Stanpole came in before I was able to, and then a nurse came in, and I was sent away.