Lloyd's third animal saga (after Kine, 1983, and last year's The Boy and The Otter) is also his weakest: the story of Zac, a magic mutt who materializes to warm the cockles of an English farmer's heart. The setting is Kent in the early years of WW II. Gruff Will Tuck is hard at work on his farm one day when a ""coarse, collie-type mongrel"" shows up whining for food. ""Damme, you're a poor beggar, scarcely fit for the knacker,"" says Wilf, and Zac--as the animal's collar has it--is soon beloved not only by Wilf, but by his wife, Rose, and daughter, Di. He's a great ratter and herds sheep like a pro--the only problem is, he keeps disappearing into the bog (the local gypsies call him ""the bog cur""). What the Tucks don't know is that Zac is having a series of nightmares graphically depicting his arrival in England--on a downed German bomber. Yes, Zac is a Nazi, although not, it should be added, a member of the S.S. But he hangs in there loyally with the Tucks, seeing them through the hard years; as victory appears on the horizon for the Allies, Zac disappears once again into the bog, and this time Wilf tracks him to the crashed German bomber: Zac has gone to die near the bodies of his first masters. . .For canine fanatics only--or for readers fond of lengthy descriptions of English farming life circa 1940.