The emotional reunion began in near silence Sunday evening as Matthew Trevithick walked through the international arrivals door at Logan Airport, home after 40 days in a notorious Iranian prison.
As relieved family members watched, the 30-year-old Hingham man strode quickly to his mother, put his arm around her shoulder, and guided her out the door and into the falling snow.
Trevithick, a Boston University graduate studying the Farsi language in Tehran, was freed from prison Saturday after Secretary of State John F. Kerry had personally pressed the Iranians to release him, according to a State Department official.
His family — worried for more than a month about his condition — did not know he was free until his mother, Amelia Newcomb, heard his voice in a phone call from Iran at 4:52 Saturday morning.
"It's been quite a strain," said his father, Paul Trevithick of Brookline.
Trevithick was released on the same day that four other Americans were freed by the Iranian government in a separately negotiated exchange of prisoners.
Trevithick left Iran Saturday on a civilian flight and arrived in Boston about 6:30 p.m. Sunday on a Turkish Airlines plane from Istanbul.
Trevithick was imprisoned clandestinely and without notice to US officials, according to the State Department official. The reason for his detention and the conditions he encountered at notorious Evin Prison remained unclear Sunday.
"We actually know very little about that," said the official, who asked not to be identified because of the sensitive nature of the negotiations. "There was never any public announcement by the Iranians of his detention and never any public announcement about the charges."
The official said it became apparent very quickly that Trevithick had been detained unjustly. "We made it clear that it would be a strong and strongly desired gesture of good will" to release Trevithick.
US officials received confirmation from Iranian authorities that Trevithick, who has traveled extensively in the Middle East, was being held after his family became concerned when they had not heard from him in early December.
His mother said Sunday that she did not have any information on why he had been detained.
Discussions to free Trevithick had been so delicate, and so fraught with the danger of collapse, that his immediate family was instructed not to tell anyone about the negotiations — or even that he was being held.
Elizabeth Trevithick, his grandmother, said the family would answer innocuous questions about Matthew with generic misdirection. "We'd say, 'Oh, he's not coming home for Christmas,' " Elizabeth said.
Newcomb said that the family heard from Trevithick about halfway through his imprisonment but that the call was made in the presence of an Iranian monitor. Although he sounded like he was in good condition, the family could not be sure because he had no privacy in which to speak freely.
Evin Prison, whose guards have gained a reputation for brutality, has been used to hold political prisoners since the reign of Shah Mohammad Reza Pahlavi in the 1970s, and later after the Islamic revolution. An Iranian-Canadian photojournalist, Zahra Kazemi, was held at Evin in 2003 and died after allegedly being tortured there.
Trevithick's release occurred the same day that four Americans of Iranian descent, including a Washington Post reporter and a Marine veteran, were freed in exchange for seven Iranians held by the United States.
That exchange occurred shortly before Iran was declared Saturday to be in compliance with the nuclear deal reached in July with Tehran. As a result, international economic sanctions were lifted against the long-isolated country.
Trevithick's freedom also closely followed the release of 10 US Navy sailors who had been detained after venturing into Iranian waters.
The convergence of several important issues — the implementation of the nuclear deal, the detained sailors, and secret discussions about the other imprisoned Americans — allowed Kerry to press for Trevithick's release directly with the Iranians, the State Department official said.
This close communication meant that the United States was able "to very quickly make it clear to the right people in the right places that it was in all of our interests" to free Trevithick "as quickly as possible," the official said.
These diplomatic channels have become exponentially more accessible since the election of Iran's president, Hassan Rouhani, in 2013, according to another State Department official, who spoke Sunday on a conference call with reporters.
As an example, the official said, "when our sailors drifted into Iranian territorial waters . . . Secretary Kerry can pick up the phone, call the foreign minister of Iran, and resolve that issue in a matter of hours. That just wasn't available to us two years ago."
Trevithick, who graduated from BU in 2008 with a degree in international relations, began language study in Tehran in September during a leave of absence from a research center he had cofounded in Turkey to study the region's humanitarian crisis.
"He loves the Middle East. He loves understanding the nuance of what goes on there," his father said. "He has been traveling the Middle East for years. He has been involved in a dangerous part of the world, so he's not naive about the risks."
Trevithick moved to northern Iraq within a year of graduation and became assistant to the provost at the American University of Iraq in Sulaimani. He also worked as communications director at the American University of Afghanistan from 2010 to 2014.
In between, Trevithick had returned to Washington to work as a research assistant in 2009 at the Woodrow Wilson International Center for Scholars.
He also was an avid athlete who won a silver medal in the Head of the Charles Regatta in 2008 and helped create an Afghan rowing team. Trevithick also coached in Iraq, according to a biography on the United States Institute of Peace website.
He wrote for The Atlantic, the Wall Street Journal, The Daily Beast, and the Christian Science Monitor.
He frequently used social media to disseminate news and information about the Middle East.
"We are profoundly grateful to all those who worked for [Matt's] release and are happy for all the families whose loved ones are also heading home," Newcomb said in a statement on Saturday.