Liam Devlin is an Irish patriot.
He was a champion of the Irish cause from his earliest days, fighting against British rule in Northern Ireland. He took his freedom-fighting stance to Spain during the height of their civil war where he fought on the side of the anti-Franco forces.
His help was then enlisted by a force that seemed incongruous to his earlier struggles, the Nazis, but since they were both fighting the British, he agreed.
Devlin is a ferocious fighter for his nation's freedom. He is also a poet, a writer, and an intellectual. After his years of struggle, as he grew more disgusted with the indiscriminant killing by the new IRA, he retired from the conflict and became a professor at Trinity College.
It is while there in his mid-60's that Devlin is approached to help his former enemy, the British Charles Ferguson. As the head of Group Four of MI-5, he twice coerced Devlin into helping his team. Even though they were politically opposite each other, there was considerable respect by Ferguson for Devlin.
This series is really two separate series as there is a thirty-four year separation in time.
The first pair of stories concerned the actions of Devlin in his helping of the Germans against the British, all in reprisal for Britain's continued dominance in Northern Ireland. In both efforts, he shared the stage with a German colonel named Steiner. They are awesome tales though they are more war stories than spy stories.
The second pair, happening in the late 70's and early 80's, are a wholly different matter. Devlin is an impressed agent for Group Four of D-15 (disguised MI-5). The work is just as exciting but the feel is understandably not the same.