It is now over 40 years since Colonel Muammar Gaddafi came to power in Libya.

During that time, hundreds of people have been detained for being critical of his regime. Many are known to have been killed, some have simply disappeared.

One of them is Jaballa Matar - a member of the Libyan opposition when he was kidnapped from his Cairo home 20 years ago. Since then his family have had just two letters from him, and fear the worst.

But recently there was a sighting of Jaballa Matar in a Tripoli prison, raising hopes that he may still be alive.

Mishal Husain spoke to Jaballa Matar's son, the award-winning novelist Hisham Matar, who has been campaigning to find the truth about his father's fate.

Impact Asia with Mishal Husain is broadcast weekdays at 1300, 1330 and 1400 GMT on the BBC World News channel. Find out more information about regional broadcast times here.