Paul Manafort, President Donald Trump’s former campaign chair, pleaded guilty to one count of conspiracy against the US and one count of conspiracy to obstruct justice on Friday. As part of his plea deal with special counsel Robert Mueller’s team, Manafort agreed to cooperate with their investigation into Russian interference in the 2016 presidential election.

According to his plea agreement, which you can read below, Manafort will work with Mueller’s team in part by participating in interviews, turning over documents, and testifying in other proceedings.

It’s potentially very bad news for Trump.

Manafort took part in the June 2016 meeting at Trump Tower with a Russian lawyer who had promised to hand over dirt on Hillary Clinton.

And Manafort had close contact with two Russians during the campaign: Oleg Deripaska and Konstantin Kilimnik. Deripaska, a notorious Russian oligarch, was once Manafort’s client. Kilimnik, meanwhile, was formerly Manafort’s longtime business associate — and possibly has ties to Russian intelligence.

The plea deal will surely help Mueller learn a lot more about those connections — and what, if anything, Trump knew about it all.

You can read the plea deal below: