Oct 21, 2014 Updated: 9:46 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
Louisa invites Martin to a dance, but he refuses, so she asks Mark; Peter Cronk causes problems on a school field trip; Martin goes to see Bodmin Moor's park ranger, Stewart James.
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