From NBC News, this is Article 2, Inside Impeachment.

I'm Carrie Dan, political editor for NBC News, filling in for Steve Kornaki.

It's Monday, October 21st, and here's what's happening.

There's another week of closed door depositions ahead of us.

Seven are scheduled, although it's not clear

if all the witnesses will appear.

But tomorrow's witness is likely to be the headliner.

Bill Taylor, the acting ambassador to Ukraine, is appearing before three house

committees on Tuesday. Taylor's name may not ring a bell, but you might remember hearing that he called any kind of quid pro quo for military aid to Ukraine, quote, crazy.

The top US diplomat in Ukraine, Bill Taylor, text the US ambassador to EU Gordon Sonland and writes this as I

said on the phone I think it is crazy to withhold security assistance for help

with a political campaign.

But this time Sonland pushes back, writing,

Bill, I believe you are incorrect about President Trump's intentions.

The President has been crystal clear,

no quid pro quo of any kind. Then Sunlin says

we should stop texting about this. Taylor left Ukraine last week for Washington DC

two days after getting an official request to appear

before Congress. So what do we know about Bill Taylor and why is his

deposition so critical to the impeachment inquiry.

Leanne Caldwell is an NBC news correspondent covering Congress. She joins us from Capitol Hill.

Hi, Leanne.

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