Christopher Guest’s new comedy series for HBO, Family Tree, is a clever show with a secret weapon — a hand puppet. Hey, hey, it’s the monkey…

Family Tree, an eight-part limited series that begins Sunday at 10:30 pm. ET, already cries out for a renewal, because it’s just getting started. The plot of the series, concocted by Guest and Jim Piddock, is set at first in the U.K., and revolves around an affable 30-year-old slacker named Tom Chadwick. When a relative dies, he inherits a trunk — and rummaging through it, he begins a quest to learn more about his distant relatives, a quest that eventually takes him to the U.S., to a branch of the family tree he never knew existed.

Tom is played by Chris O’Dowd (far left), who cut such a likable figure in both Bridesmaids and HBO’s Girls. That affability serves him well here, because he’s the guy who takes us on this meandering but entertaining journey. In the first four episodes, he’s accompanied on his search by childhood buddy Pete (Tom Bennett), and urged on by his father (Michael McKean (left), Guest’s fellow Spinal Tap bandmate) and his sister, Bea.

Bea is played by Nina Conti (right), the daughter of actor Tom Conti, whose TV version of The Norman Conquests is one of the all-time great miniseries. Clearly, talent didn’t skip a generation in the Conti family, because Nina, through surrounded by whip-smart comic actors, steals almost every scene in which she appears as Bea.

Of course, she has a little help. Specifically, a hand puppet called Monkey.

The first episode of Family Tree explains Bea’s co-dependence on her hand puppet. After a traumatic experience as a child, a shocked-into-silence Bea was given the monkey puppet and encouraged to speak through it. She did, and never stopped.

The monkey — which is admittedly reminiscent of Mel Gibson's alter ego in The Beaver — is also a constant, unvarnished truth-teller, as rude, and as uncomfortably funny, as Robert Smigel’s Triumph the Insult Comic Dog. Bea and her monkey could be a show all by themselves, but they’re only one element of Family Tree. Other elements include running parodies of British TV shows Tom’s dad enjoys watching — and, of course, the running plot about Tom’s version of Roots.

Eventually, this season of Family Tree will take us to the States — where Guest (right, with O'Dowd), who has shaped this series as the tightly outlined, improvisation-encouraging TV equivalent of his Best in Show and Waiting for Guffman movies, will reunite with such usual cohorts as Fred Willard and Bob Balaban.

But even before then, Family Tree is a quietly satisfying, impressively unpredictable series — one that proves so involving, it already seems prudent to encourage HBO to order new episodes.

I don’t know where Tom’s search for his ancestors is headed, or what will happen or be said and done along the way. But I know this much: I’d like to stay around for the ride.

For a full review, see or hear my report on NPR’s Fresh Air with Terry Gross.