When Michael Cohen walked past the “something huge is happening” metal barricades and into the federal courthouse in downtown Manhattan on Tuesday to plead guilty to a litany of crimes, we got a first hand view of one of the ways Cohen had earned his title “fixer” for Donald Trump for many years. One of the crimes to which the president’s formerly loyal-I-would-die-for-you fixer pleaded guilty was to helping arrange an illegal scheme whereby women would be paid off for their silence to keep stories about Trump’s affairs out of the media prior to the election.

But that wasn’t all.

Cohen also gave testimony under oath in front of a federal judge that the president directed him to do that. But that’s not all, either. He also pleaded guilty to basically cooking the books of the Trump Organization to cover up those hush money payments as legal fees and “tech services.”

But even that’s not all.

We now know from the charging document (called an Information) to which Cohen pleaded guilty, that several other people, identified but not named, were involved in that scheme. The Information identifies a “Chairman of a Media Company,” and Executive-1 and Executive-2 of what is clearly the Trump Organization, as participating in this scheme. Based on reporting and the facts in the Information, it’s clear that the media chairman is David Pecker of American Media, Inc. (the National Enquirer), a longtime ally of Trump, and that Executive-1 is Allen Weisselberg, chief financial officer of the Trump Organization.

And we now know, based on further reporting, that both of those men received some kind of immunity deal in exchange for their cooperation. (Weisselberg’s immunity was restricted to grand jury testimony in the Cohen case, AP reported.) Usually, immunity entails giving essentially a pass on prosecution to someone who has some criminal exposure but is less culpable than people about whom they can testify.

So, the question is, who have Pecker and Weisselberg given information about to authorities? We know one person, Cohen— presumably that is one of the reasons he took a relatively quick plea. Is that it? We think not. First of all, federal prosecutors don’t give immunity in any form lightly. And it seems unlikely that the Southern District of New York needed to immunize these two witness just to charge Cohen. They seem to have other significant evidence against Cohen including his own statements and recordings that he made of him and Trump discussing this scheme. Second, there are several different state entities investigating this scheme, the New York Attorney General and the Manhattan District Attorney’s Office. These various entities would not likely be vying to investigate crimes which have already been fully successfully prosecuted.

So, who should be worried? We know from the Information at least some of the individuals and entities who should be concerned: Executive-2 of the Trump Organization, the Trump Organization, and possibly “one or more members of the campaign” who coordinated with Cohen.

“ It seems unlikely that the Southern District of New York needed to immunize these two witness just to charge Cohen. ”

Now that Cohen has pleaded guilty, he may also be a source of information for investigators building a case against these subjects and possibly others. Cohen—surprisingly—pleaded guilty to what prosecutors call a “straight up” plea agreement, not a cooperation agreement. Under his agreement, Cohen faces a presumptive sentence of roughly four to five years in federal prison. (There is no parole in the federal system; the only reduction a defendant can get is 15 percent off for good behavior in prison.) Given that Cohen seems determined to avoid or minimize his jail time, and given that he has information that would seem to be relevant to prosecutors, why would he plead guilty without any assurance that cooperation can help him get a lighter sentence?

It is true that cooperation can occur at any point in an investigation, including after entering a non-cooperation guilty plea as Cohen did on Tuesday. In fact, cooperation can occur after a guilty plea or a trial. There even is a mechanism called Rule 35 by which a defendant can receive a sentencing reduction after he is originally sentenced. So it is by no means too late for Cohen to come onboard with the Southern District and/or other prosecutors, including special counsel Robert Mueller. If Cohen does successfully cooperate moving forward, then he would be in position to receive a significant sentencing benefit.

But, it takes two to cooperate. There seems to be no doubt that Cohen is interested. Even after Cohen’s plea, his attorney Lanny Davis did another round of media advertising his client’s testimonial services. But the Southern District seems tepid at best: if it truly was eager to sign up Cohen as a cooperator, they likely would have begun proffering him many weeks ago. So why hasn’t that happened yet?

First, Cohen is an exceptionally slippery character. All cooperators are problematic, to an extent. That’s why they are cooperating witnesses and not just plain witnesses. Cooperators, by definition, already have committed crimes and are willing to implicate others in those crimes. Second, Cohen likely has been committing crimes for many years, perhaps coinciding with the start of his work as Trump’s all-purpose fixer. Cohen therefore carries much baggage with him into the proffer room, and it might be too much for him to come clean about.

But it also seems unlikely that Cohen simply will accept his fate and serve four or five years in prison. To that end, Cohen still has a few cards to play.

First, even without a cooperation agreement with the Southern District, Cohen’s lawyer can argue to the sentencing judge for a lenient sentence based on whatever assistance Cohen provides to the government, known in federal parlance as the catch-all “3553(a) factors.”

This might explain why Cohen seems so eager to be subpoenaed by anybody who will have him. If asked or subpoenaed to testify in any proceeding—trial, grand jury, even legislative—most people like Cohen who have committed crimes would invoke their Fifth Amendment right not to incriminate themselves. (By pleading guilty to certain federal crimes, Cohen no longer has a Fifth Amendment claim as to those particular crimes—,but he may have committed additional state or federal crimes for which he does not yet have coverage, and can still plead the Fifth). Yet, reportedly, when Cohen received a subpoena from the New York State Tax Department the day after his federal guilty plea, Cohen personally called in response to the subpoena to say that he would be available. Similarly, Davis told MSNBC’s Chuck Todd on Wednesday that Cohen would be responsive to any subpoenas issued to him and would testify truthfully.

So, the next step in this investigation will likely include not only Weisselberg, Pecker, and all of the physical evidence prosecutors have, but also, in some form, Cohen. This must have many people, including Trump, very concerned.