Is this a reference to mystery-man “Misha”? To Tsarnaev’s wife, who allegedly seemed not as surprised by what happened as she should have been? To some as-yet unnamed figure who showed these two degenerates how to build something a little more advanced than Al Qaeda’s magazine described? Or to someone else?

Rep. Dutch Ruppersberger (D-Md.) told ABC News on Sunday that the FBI is investigating “persons of interest” inside the United States connected to the Boston bombing.

“There are persons of interest in the United States,” said Ruppersberger, the ranking Democrat on the House Intelligence Committee. “We’re looking at phone calls before and after the bombing, this type of investigation.”

House Intelligence Committee Chairman Mike Rogers (R-Mich.) added, “There are still persons of interest in the United States that the FBI would like to have conversations with.” But “the big unknown,” he said, was the six months Tamerlan Tsarnaev spent in Russia.

Christian Caryl of the New York Review of Books claims to have found Misha, who told Caryl that he hadn’t spoken to Tsarnaev in three years, that he’s cooperating with the feds by giving them his phone and computer, and that “If I had been his teacher, I would have made sure he never did anything like this.” Supposedly the feds are about to close his case. As one mystery ends, though, another begins: How can it be that the feds didn’t find out from Russian intelligence until recently that Tamerlan talked jihad with mama Tsarnaev two years ago?

The vague substance of the phone calls was shared only a few days ago with U.S. officials investigating the April 15 bombing near the finish line of the Boston Marathon, which killed three people and injured more than 260.

“It was two very general conversations not shared until recently,” said the official, who spoke on condition of anonymity because he was not authorized to share details of the investigation.

No explanation was given for why Russian authorities waited so long to tell U.S. authorities about the telephone calls. The information could have provided an additional reason for U.S. authorities to heighten scrutiny of bombing suspect Tamerlan Tsarnaev, 26.

So that’s what Mike Rogers meant a few days ago when he grumbled about the Russians not telling us everything they knew. But wait — didn’t Russian intel tell the FBI in 2011 that Tamerlan and his mother were suspected of being “religious extremists,” in CBS’s words? What’s the difference between that and the two of them having a “general” conversation about jihad? Surely the feds could have inferred from the Russians’ worries that Tamerlan was preparing to walk the walk, not just talk the talk. I’m guessing they looked the other way because they figured “extremism” meant Tsarnaev would end up taking off for Chechnya to go fight there, not bomb marathon crowds here in the U.S. That’s … really stupid, but if surveillance resources are scarce, you can sort of understand why a budding jihadi who appears to be focused on Dagestan would be a lower priority.

One more mystery. Does this explanation of Dzhokhar Tsarnaev’s preternatural calm after the bombings really add up?

“It’s scary to think that he was around here, listening to everyone talking about the bombers and stuff like that,” Bobby Kedski, a sophomore at the University of Massachusetts Dartmouth, said of Dzhokhar, a fellow student there, whom he saw working out in a campus gym on Tuesday night. “He was just amongst us, taking it all in. It’s scary to think about that.”

Slipping back into a routine after committing a crime, even an atrocity, is fairly typical behavior, said Dr. Stuart W. Twemlow, a retired professor of psychology at Baylor College of Medicine in Houston. He works on threat assessment with the F.B.I. and helped on the Columbine shootings, among other cases.

A return to business as usual helps a criminal “blot out the horror with which he was associated,” Dr. Twemlow said.

“That is a normal, dissociative response,” he said, adding that the younger brother, whose movements were more public, had most likely “denied and compartmentalized what he had just done.”

Yeah, but he hadn’t dissociated completely. There were sly tweets afterward about how there “ain’t no love in the heart of the city” and how he’s a “stress free kind of guy.” In the photos at the marathon, he’s the one with an enigmatic smile on his face, not Tamerlan. He wasn’t so overwhelmed by what he’d done that he surrendered meekly when his brother, whom he claims was the mastermind, was pinched by Boston cops. He actually drove over him in his haste to get out of there and stay on the run. What’s the difference between a criminal who resorts to routine in order to cope with his guilt and a criminal who resorts to routine because he’s sociopathically untroubled by his crimes?

By the way, if you missed it on Saturday, enjoy the NYT’s new quasi-theory that Tamerlan might have turned sour because new rules barred non-citizens from fighting in the Golden Gloves or something.