A heat machine comprising a displacer reciprocating within a housing. The displacer incorporates first and second independent, co-axial, overlapping regenerators. A first working volume is formed between the displacer and the housing at a hot end of the heat machine. Second and third working volumes are formed between the displacer and the housing at a cold end of the heat machine. A partition separates the second and third working volumes. A gas flow path exists from the first working volume to the third working volume via the first regenerator, the second working volume, a gas path within the partition, and the second regenerator.