A turbine module (100) for a heat engine (104) wherein the turbine module (100) defines a working fluid flow duct (60) between a turbine module inlet (110) and a turbine module outlet (114) configured to expand a working fluid as the working fluid passes along the working fluid flow duct (60). The turbine module comprises a first heat exchanger (37) and a turbine rotor stage (24) each provided in the working fluid flow duct (60). The first heat exchanger (37) is provided in flow series between the turbine module inlet (110) and the turbine rotor stage (24); and the turbine stage (24) is provided in flow series between the first heat exchanger (37) and the turbine module outlet (114). The first heat exchanger (37) defined by a wall (126) having an external surface (182) which is located in the working fluid flow duct (60). There is provided a heat supply unit (136) which defines a portion (140) of the working fluid flow duct (60) in flow series between the turbine rotor stage (24) and turbine module outlet (114). The first heat exchanger (37) is in heat transfer communication with the heat supply unit (136), and the first heat exchanger (37) is configured such that it is operable to transfer heat received from the heat supply unit (136) to the working fluid (150) passing the first heat exchanger (37).