Martin believes Louisa may be anaemic after she passes out in front of her class. A young girl is treated for hyperactivity and it's suspected that she's been taking her Mum's diet pills. After the horror and shock of discovering his fiance Julie's secret, Constable Mark Mylow has left - PC Joe Penhale (John Marquez) arrives in Portwenn to replace him, arousing attention from the doc, who discovers him unconscious at the wheel of his police car.