Welcome to The Investigation.

I'm Chris Vlasto, senior executive producer here at ABC News, and I'm joined by my co-host,

senior editorial producer, John Santucci, who covers all the aspects of the Trump

administration.

A busy week ahead in Washington as the House impeachment inquiry begins its second week of public hearing with eight more witnesses.

So we have our congressional reporter, Catherine Foulders, who knows everything that's going on in Capitol Hill.

So, Catherine, who are the witnesses that we look forward to this week?

There's two that I'm looking at. Obviously, it's Binman Tuesday and Sunlin on Wednesday, right?

Yes, I think you have those two. We have eight total this week. So those two we're going to be

paying close attention to. And then I think it's important to watch.

There's three people who will be testifying publicly who were actually on that July 25th call.

So Republicans aren't really going to be able to make that argument anymore that there's no firsthand knowledge

because you will be talking to witnesses who heard what the president said, and there's some

question about whether that's the full transcript or not. Gordon Sondland, though, he's going to be

the center of this. He's the EU ambassador, and he's raised a lot of questions from Democrats and

Republicans because, as you know, he's already had to revise his testimony twice. At first, he said he didn't think a holdup of military aid was conditioned on investigations. And then he said, oh, wait a second, it actually was. And I told an advisor to President Zelensky that, in fact, it was. He uses the word presumed in that revision, so Republicans will obviously capitalize on that.

But he's important because Morrison, Tim Morrison, ex and a C official whose deposition came out over the weekend that we were all pouring through.

Morrison mentioned Sunland many times.

He talks about how he didn't have much confidence in him, but he also brings up a

variety of separate phone calls that Sondland says he had with the president. He says there's at

least five phone calls. And it's important on those five to remember the timeline. Sunlin

originally said, you know, he wasn't talking about the holdup of aid with

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