Any Old Iron - S8.E4

Mr Middleditch has come in to St Aidan's hospital, accompanied by his wife, for a routine operation. Noticing that Mrs Middleditch looks unwell, the hospital decides to give her a blood transfusion. Distracted by the attentions of a rich divorced playboy, who has promised to marry her, Susie Dixon administers the wrong blood, which later results in serious consequences for both her and the patient.