Jul 30, 2014 Updated: 7:15 PM
A modern, edgy drama full to the brim with passion, politics and peril. MI-5 leads us into the dangerous world of Britain's top-secret security agency, and into the lives of people who must lie, and sometimes die, for a living.
VISIT THE BBC's MI-5 WEB SITE
Martin's estranged parents visit; school secretary Maureen Tracey visits the doctor for a thyroid problem; Danny Steel collapses and needs emergency surgery to save his life.
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