The FBI just gave Donald Trump a gift wrapped in an October surprise.

In a letter to members of Congress, Director James Comey said the FBI, through “an unrelated case,” has “learned of the existence of emails that appear to be pertinent” to the investigation of Hillary Clinton’s private email server—an investigation that the FBI had concluded in July with a recommendation not to pursue criminal charges against the Democratic nominee. Comey said the FBI is now taking steps to determine whether these emails contain classified information. The investigation, in the words of Speaker Paul Ryan, has been reopened.

Eleven days from the election, this is terrible news for Clinton. Perhaps no issue has hurt her more this cycle than her use of the private email server during her tenure as secretary of state, and she has apologized for it. In September, before the release of a tape showing Donald Trump bragging about sexual assault, her lead in the polls over Trump collapsed in large part because of questions about her trustworthiness. It didn’t help that media organizations tended to equate Clinton’s controversies with the far more egregious controversies that disqualify Trump from being president.

It also doesn’t help that Comey has thrown out a totally opaque description of this supplementary investigation to the public. (Some are debating whether, technically speaking, the investigation has been “reopened.” It remains unclear.) Trump and his surrogates will surely use Comey’s letter to stoke dark suspicions about Clinton that in all likelihood are unwarranted. If Clinton wants to be president, it looks like she’ll have to walk through the fire of yet another messy controversy to get there.

Update: Trump is already making hay of Comey’s letter, despite its lack of details. In a statement, he praised the courage of the FBI for “right[ing] the horrible mistake they made.”