Arrows of Fury
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Centurion Marcus Aquila has to keep his head down as another Roman comes over to Britain trying to track him down after his family are branded traitors by the emperor.
His higher-up friends who know his secret manage to keep him out of the way by sending him and his century off scouting around the countryside, where (as in book 1) he runs into all sorts of barbarians and kills them.
The second half gets more into the action and has some tense moments.