A bipolar plate assembly for use in a PEM fuel cell having an anode plate and a cathode plate together to define flow fields on the exposed faces thereof and a coolant volume therebetween. Each of the flow fields have a transverse inlet leg in fluid communication with the inlet header, a serpentine flow field extending from the transverse inlet leg and a transverse exhaust leg in fluid communication with the exhaust header. The plates further define a tortuous coolant flow path in the coolant volume.