Callan (Edward Woodward), having been taken off active duty because his superior, Hunter (Eric Porter), believed he wasn't performing as well as he used to, is now being asked to come back for a single, specific assignment. The task involves eliminating a man named Schneider. Acceptance of this job would guarantee his return to the fold without any further discussion. However, Callan isn’t simply someone who carries out orders; he needs to understand more about the person he's supposed to target, and so begins investigating him. This man (Carl Möhner) enjoys recreating Napoleonic battles with meticulously crafted armies of painted cast-iron soldiers, and leads a seemingly ordinary life alongside his wife (Catherine Schell). Callan’s employer isn’t satisfied with his approach and decides that his replacement, Meres (Richard Egan), should develop an alternative strategy – one where Callan might become expendable. What follows is a thriller that moves along at a reasonable speed, although it can be somewhat perplexing, containing nearly every trope imaginable except for a poisoned umbrella. Woodward and his associate, Lonely (Russell Hunter), have returned to their roles from the popular ATV television series of the late 1960s, and in many respects, this feels like an extended episode from that show. It's perfectly acceptable, with good production quality, and possesses a certain depth.

Source on TMDB