Four years ago, a young, curious couple set out on the adventure trek of a lifetime - an exotic backpacking trip through Kyrgyzstan, Kazakhstan, and Tajikistan.

But for reasons still undisclosed, Caitlan Coleman, 31, of York County, and her Canadian-born husband, Joshua Boyle, 33, wound up in Afghanistan, where they were kidnapped by a militant Islamist group.

On Monday, a video was released showing Coleman pleading to President Obama and President-elect Donald Trump to help free the couple and their two sons born during their captivity. The video has yet to be officially authenticated.

In response, Sen. Bob Casey (D-Pa.) said Wednesday that the video, though difficult to watch, could be seen as a "positive sign" the family is alive.

And Gov. Tom Wolf expressed "deepest sympathy" for the families.

Casey said in an interview that he and his staff have been in "constant communications" both with Coleman's family in Stewartstown, and with the White House group that monitors hostage takings.

The senator said he had been briefed by the White House about the captured family as recently as three weeks ago, but declined to elaborate.

While watching the video, said Casey, he was struck by how relatively healthy the family seemed - especially the children. "They looked better than I would've thought," he said.

Casey praised the Coleman family as "a model of persistence and determination" through "the most horrific of situations," and added, "I hope our government can get [the couple] home."

Coleman and her husband have appeared previously in videos, but the one released Monday was the first showing their children.

Clearly reading from a script, Coleman said ominously, "My children have seen their mother defiled."

She appealed to Obama to not "become the next Jimmy Carter," referring to Carter's failure to release hostages from Iran when he was president.

"We have waited since 2012 for somebody to understand our problems, the Kafkaesque nightmare in which we find ourselves," she said in the video.

Coleman was pregnant with the couple's first son in late 2012 when she and Boyle were kidnapped by the Haqqani network, a militant Islamist group affiliated with the Taliban. That child was born in 2013; their second son two years ago.

The months-long tour in a part of the world few westerners ever see, certainly had risks. But the couple, travel junkies, who married on a hike through Central America in 2011, thought they had the experience to handle it, according to their families.

They departed July 4, 2012, and were due to return that December.

But two months into the trip came an ominous email to Caitlan's parents, sent from an internet café in what Boyle described as an "unsafe" part of Afghanistan.

They had promised that Afghanistan, among the least stable of the fractious "stans," would not be on their itinerary. What were they doing there?

For a time, there was no correspondence. Then came a horrifying twist: U.S. government officials believe the two were kidnapped in Wardak Province, an insurgent stronghold near Kabul, by members of the Taliban affiliate known for scooping up westerners and demanding ransoms or prisoner exchanges.

In 2013, Coleman's parents received two videos in which the couple is seen pleading to be released from captivity. In the years since then, sporadic videos and letters have painted a mixed picture of their captivity, and efforts by government and private individuals to win their freedom have foundered.

In correspondence that was somehow delivered through intermediaries to Boyle's parents in Ottawa, and later reported on in the Toronto Star, Boyle explained how in 2015 he had delivered his second son in darkness, while holding a flashlight in his mouth.

"The astonished captors were good and brought all our postpartum needs," he wrote, "so he is now fat and healthy, praise God."

If that was reassuring, the threat outlined in a YouTube video released this past August, was anything but.

Once again, reading from a script, Boyle said that if the Afghan government did not stop executing Taliban prisoners, he and Coleman would be killed. Canada's press reported that the August 29 video coincided with an Afghan court ruling that Anas Haqqani, a son of the network's founder, be put to death for his role in raising funds for the militant group.

"They will execute us, women and children included," Boyle pleaded on the video, "if the policies of the Afghan government are not overturned either by the Afghan government or by Canada, somehow, or the United States."

Coleman's friends in rural Stewartstown, the York County community where she was raised and home schooled, have described her as a woman shaped by rural values, with a bighearted curiosity about the wider world.

An October Philadelphia magazine article reported she got to know Boyle online, and they bonded over a shared love of "Star Wars."

Boyle, the son of a Canadian taxation judge, attended a Mennonite school. Alex Edwards, a friend who wrote a blog about Boyle after he was kidnapped, described him as "charismatic, principled, and passionate about his causes, whether they were political, intellectual or personal."

Boyle, described by friends as having an interest in Islam and the Middle East, was married for a year to Zainab Khadr, whose father, killed in Pakistan in 2003, was suspected of links to al Qaeda, and whose brother, Omar Khadr, was the only Canadian citizen ever held at the U.S. prison in Guantánamo Bay.

Omar Khadr was 15 when he was arrested in Afghanistan for allegedly throwing an explosive device at American troops. In Canada, Boyle helped organize Zainab Khadr's hunger strike in 2008 to raise awareness about her brother's case. For a time, Boyle was the Khadr family spokesman. Omar Khadr was released and sent back to Canada in 2012, two years after Boyle and his sister were divorced.

Despite the intrigue of that backstory, Canadian government officials have said they believe Boyle's kidnapping is coincidental, and unrelated to the Khadr family tie.

In the video released Monday, Coleman said her situation is dire, her captors serious.

"Their group will do us harm and punish us," she said, to which her husband added, "they really will not settle this until they get what they are demanding."