DOWN THE RABBIT HOLE:

Trump was in Waterloo, Iowa, for a caucus-day rally at the Five Sullivan Brothers Convention Center -- named for five local siblings who had been assigned to the same Navy cruiser in World War II. They all died when the ship went down at Guadalcanal.

Trump had stopped his rally to do something presidential candidates don't normally do. He was giving away money.

Arnold and Tim, whom he had called to the stage, were from a local veterans group. Although their big check had Trump's name on it, it wasn't actually Trump's money. Instead, the cash had been raised from other donors a few days earlier, at a televised fundraiser that Trump had held while he skipped a GOP debate because of a feud with Fox News.

Trump said he had raised $6 million that night, including a $1 million gift from his own pocket. Now Trump was giving it, a little at a time, to charities in the towns where he held campaign events.

"See you in the White House," one of the men said to Trump, leaving the stage with this check that married a nonprofit's name and a campaign's slogan.

"He said, 'We'll see you in the White House,' " Trump repeated to the crowd. "That's nice."

After that, Trump lost Iowa.

He won New Hampshire.

Then he stopped giving away money.

But as far as I could tell, just over $1.1 million had been given away. Far less than what Trump said he raised. And there was no sign of the $1 million Trump had promised from his own pocket.

So what happened to the rest of the money?

It sounded like an easy question that the Trump campaign could answer quickly. I thought I'd be through with the story in a day or two.

I was wrong.

That was the start of nine months of work for me, trying to dig up the truth about a part of Trump's life that he wanted to keep secret. I didn't understand -- and I don't think Trump understood, either -- where that one check, and that one question, would lead.

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