The father of journalist John Cantlie, who is being held by Islamic State militants, has appealed for his son's release.
Paul Cantlie spoke of his family's "despair and helplessness" after seeing him on a video released on the internet.
Delivering his appeal in a video, he said: "To those holding John, please know that he is a good man.
"He sought only to help the Syrian people and I ask you from all that is sacred to help us to allow him to return safely to those he loves and those who love him."
Paul Cantlie and his son, John
Speaking with the help of a voice aid from a hospital bed, Mr Cantlie said the family experienced "great reilef" when they saw John in a televised broadcast - but this feeling turned to "despair".
Referring to the moment he saw John in the clip, Mr Cantlie said: "For the first time in almost two years, we saw John when he made a televised broadcast during which he told viewers that he was still a prisoner of the Islamic State and that maybe he will live and maybe he will die.
"As a family we experienced great relief seeing and hearing John and knowing that he is alive, but this was followed by the feeling of despair and helplessness."
Hostage Mr Cantlie, who has worked for newspapers including the Sunday Times, was seized in northern Syria, where he had been working as an independent photo journalist, "seeking out the true story of the suffering of the Syrian people and ensuring the world was made aware of their plight", his father said.
Speaking about his son, Mr Cantlie said: "John felt a strong need to help in the best way that he could: as an impartial and respected journalist he knew that he could make a difference by acting as a platform for the world to listen to and take notice, using his journalistic skills for the good of the people; as a friend and as a civilian. I have had many messages saying they cannot conceive what we, his family and all those who love him, must be feeling."
He spoke about the pride he has for his son, and said nothing would bring him "greater joy" than his release.
John Cantlie, the journalist being held by IS militants
"Speaking entirely for myself, this is not how I had imagined I would be passing my 81st year. I want John to know how very proud I am of him. I can think of no greater joy than seeing him again, released and allowed to return to those who love him," he said.
Mr Cantlie said he and his family are trying to communicate with the Islamic state to deliver an "important message regarding John" and said they can only hope that it has been received but they have had no response.
Addressing his son's captors, he said: "To those holding John: please know that he is a good man, he sought only to help the Syrian people and I ask you from all that is sacred, to help us and allow him to return home safely to those he loves and those who love him."
The Islamic State group last week released a video showing the British journalist who says he is a prisoner of the extremists.
The group which now controls roughly a third of Syria and Iraq has beheaded two US journalists and a British aid worker, and has threatened to kill another British hostage.
The just over three-minute long clip released last Thursday by the Islamic State group's media arm, Al-Furqan, was different than previous videos.
Entitled "Lend me Your ears," it is previewed as the first in a series of lecture-like "programs" in which Cantlie says he will reveal "the truth" about the Islamic State group.
Wearing an orange T-shirt and sitting behind a desk, Cantlie criticised the war on the Islamic State group and said he and other British and US hostages have been abandoned by their governments. Cantlie's name has not been mentioned among foreign hostages held by the group.
He was briefly held up by Islamic extremists along with a Dutch photographer in Syria in July 2012.
No Islamic State fighters appear in the video, which was posted online by users associated with the Islamic state group and reported by the SITE Intelligence Group, a US terrorism watchdog.
In addition to beheaded US journalists James Foley and Steven Sotloff and British aid worker David Haines, the Islamic State group has threatened to kill Alan Henning, a British former taxi driver who was taken captive in December shortly after joining an aid convoy and crossing the border from Turkey into Syria.