Sometimes an actor takes an average role and, through skill, technique and pure presence, transforms it into something much better. Once in a great while, an actor takes a very good role and produces something extraordinary.

That's what occurs in 'Homeland' (10PM ET Sunday, Showtime), which would be worth watching if all it had going for it were the tremendous work being done by Claire Danes and Damian Lewis. But 'Homeland' also manages to be both an addictive espionage thriller and a compelling character study, as well as a well-constructed exploration of the difficulties and ambiguities of fighting terrorism a decade after Sept. 11. Without a doubt, it is one of the finest new shows of the year.

Danes and Lewis both portray guarded, damaged characters who have trouble knowing whom to trust, and the parallels and contrasts between them are fascinating. Lewis plays Nicholas Brody, a Marine who returns home after eight years as the captive of Islamic radicals, and his wariness may be the result of understandable re-entry difficulties -- or it may indicate something more sinister.