Moondyne Joe did not rob anyone else, though he did do some wrong things and was sent back to jail a few more times. In January 1879, he married a widow named Louisa Hearn, and they spent some time looking for gold near Southern Cross. In 1881, while looking around Karridale, he discovered Moondyne Cave. In his later years, he began acting strangely, and became mentally ill. He died of senile dementia in the Fremantle Lunatic Asylum (now the Fremantle Arts Centre building) on 13 August, 1900. He was buried in Fremantle Cemetery.