There's an outbreak of measles in Tannochbrae. Dr Cameron is laid up in bed convinced that he's contracted it too, but Dr Finlay diagnoses a common cold. Corporal Ian Grant goes AWOL from a military hospital with an infected leg that the Army surgeon intends to amputate. In the opinion of Finlay and specialist Sir William Duffy this is not necessary. Can the various medics reach a diagnosis for Cameron and Grant?