Immunotherapy is a pioneering new cancer treatment that aims to boost the body's natural defences to fight the disease. Showing success in trial phases, it often has fewer debilitating side effects than chemotherapy. This documentary follows a small group of patients over one summer as they undergo the treatment at the Royal Marsden NHS Foundation Trust in London, meets them between sessions as they go about their daily lives and finds out whether immunotherapy has given them the most precious gift of all - more time