Indulf was an ambitious nobleman, descended from past Kings of Scotland. In 954, upon Maol Chalvim I's death, he seized the Scottish throne through a sudden coup while the late king's sons, Duff and Kenneth, were attending their father's funeral at Iona, and took the late king's widow, Queen Katharine, as a hostage. Duff and Kenneth were forced to yield to Indulf's usurpation, and he held the Scottish throne, with Katharine and her new-born son Prince Malcolm, as his prisoners until 962.
In that year, with the help of Robbie, Prince Malcolm escaped, and Katharine threatened to throw herself off the battlements unless Indulf surrendered to Duff and Kenneth. Realizing that with her death, he would be without a hostage, Indulf agreed to yield, and with his rivals' permission, abdicated and went into exile to Ireland with his son Culen. Indulf died there, some time between 962 and 967.
Real World Background
Indulf was a real Scottish king, the son of Constantine II, who was King of Scotland from 900 to 943. Little is known about him beyond the dates of his reign, and his place in the royal Scottish pedigrees. He did indeed abdicate in 962; in actual Scottish history, he then retired to a monastery, but was soon forced out of retirement to battle the Vikings at Findochtry in Moray, where he was slain.