On June 8, as he prepared to leave Washington, D.C., for the G7 summit in La Malbaie, Quebec, Donald Trump bid adieu to the Mueller investigation. “I am heading for Canada,” he wrote on Twitter. “From there I go to Singapore and talks with North Korea on Denuclearization. Won’t be talking about the Russian Witch Hunt Hoax for a while!” Miraculously, the president has kept his word. For nearly a week now, Trump has made no mention of Robert Mueller, or the F.B.I., or the Department of “Justice”, as he likes to call it, putting the word in scare quotes. Yet as he settles back into the West Wing, after a head-spinning week of idiosyncratic diplomacy, the afterglow of his photo op with Kim Jong Un is already fading in the harsh light of Washington as the special counsel closes in.

Last month, the president’s loquacious lawyer, Rudy Giuliani, seized on Trump’s upcoming meeting with Kim to punt a looming confrontation over an interview with Mueller. “If they put this thing on, and [they] probably [would] have to do it in the next two days,” he told CNN. “We literally can’t get much done until after the 12th, until after he comes back from Singapore.” But now, with the summit in the rearview, the pressure is back on. Within the next month, the special counsel is reportedly expected to conclude the obstruction of justice portion of his probe, and an interview with Trump is the final missing piece that will allow him to determine whether the president acted with “corrupt intent” when he fired former F.B.I. Director James Comey and engaged in other activities under federal scrutiny. As William Jeffress, who worked on the Valerie Plame leak case, explained to me earlier this year, “If Mueller is going to fulfill his mission, I think it’s absolutely key” that he speak to Trump.

After months of fraught back-and-forth with Trump’s legal team over an interview with the president, Mueller has not given up on securing a sit-down with one of his most important witnesses. Citing current and former officials, Bloomberg reported Wednesday that Mueller is intent on quickly resolving the issue with Trump’s lawyers. Whether Giuliani will acquiesce to allow Mueller to interview his client remains an open question. But wielding the power to subpoena the president, Mueller has a nuclear option. And while a subpoena would assuredly result in a contentious court battle, legal experts I have spoken with over the past several weeks largely agree that Mueller would win in a courtroom showdown. “Every president who has been served with a subpoena has complied in some sense, although always with a wrinkle,” Josh Chafetz, a constitutional-law professor at Cornell Law School, told me recently. But in the end, he added, “the judiciary has consistently held that presidents are subject to subpoena.”

Despite Trump’s extraordinary assertions that he cannot obstruct justice, cannot be subpoenaed, and has the absolute power to pardon himself, the hard reality of the Mueller probe is not lost on Trump. As my colleague Gabriel Sherman reported this week, Republicans close to Trump say he is deeply concerned that the Russia investigation is at an inflection point. “It’s going to hit the fan pretty soon,” a friend of the president said. Indeed, there is a sense in Washington that the special counsel’s work is entering a final phase. The president’s former lawyer and fixer, Michael Cohen, has told friends he expects to be arrested any day now, according to a source with knowledge of the situation. (Cohen has denied saying this.) Former Trump campaign manager Paul Manafort is likely to be imprisoned after allegedly violating the terms of his bail. Both men are probably targets for the special counsel to flip.