An opera to be staged in Adelaide will be based on the cold case disappearance of the Beaumont children.

It will be performed in 2016, 50 years after Jane, Arnna and Grant Beaumont were last seen alive.

Innocence Lost is about a fictional friend of one of the three siblings who disappeared from Glenelg beach on Australia Day in 1966.

The opera by Adelaide production company SINGular Productions is an adaptation of a novel Time’s Long Ruin.

Company artistic director Adam Goodburn said he drew his inspiration from the way the disappearance case changed how parents supervised their children.

“Before then it was OK for kids to be wandering around til, you know, eight o’clock at night and doors were left unlocked and so on and then there just seemed to be this change, this sort of almost loss of innocence, hence the title,” he said.

He said the opera told a story of friendship, love and loss.

“It follows the story of a little boy who was the best friend of the oldest girl who disappeared and how he deals with the loss of his friends and how the community and the state deal with the loss as well,” he said.