Obsessive-compulsive Mrs Tishell returns to the village, and her affection for Martin quickly disappears when he refuses to pass her fit for work. As if he didn't have enough on his plate, the grumpy doctor must also face his fear of blood when tests show that Lorna has a high level of ferritin, which is placing a strain on her heart and liver. Meanwhile, PC Penhale hopes to be selected for an elite police squad by taking part in a survival training course - but ends up shooting himself in the foot.