In Search of the Miraculous, the last and most poignant work by the Dutch-born artist Bas Jan Ader, was intended to be a performance in three parts. On the afternoon of July 9, 1975, the 33-year-old artist said goodbye to his American wife and set sail from Cape Cod on a solo voyage across the Atlantic. His boat, the Ocean Wave, was only a little over 12ft in length, the smallest craft in which such a feat had ever been attempted. On the night before his departure, he arranged for a student choir to sing sea shanties around a piano in the gallery of his Los Angeles dealer. The voyage was to be the central element in the performance. To end it, Ader planned a second sing-song when he reached Falmouth eight to 10 weeks later. But, after three weeks, radio contact with his boat was lost. Although it was spotted 60 miles out to sea and again near the Azores, he was never seen again. To this day, no one knows whether Ader was swept to his death by a freak wave, became disorientated and jumped overboard, or whether, from the first, his intention in staging his last work had been to commit suicide. The body of work Ader left behind is extraordinary, but it isn't extensive - only a few short films (most of which were made in a single weekend) plus some photographs and several performance pieces. In short, he is a classic cult figure, an artist's artist. His work was enormously influential, but of limited popular appeal. At least, that's what I thought until I saw All is Falling, the heartbreaking retrospective of his work at the Camden Arts Centre.