It's 1942, with the German armies occupying most of Europe. On the rocky banks of that great Scottish lake called Loch Ness, young Angus MacMorrow (Alex Etel) finds a strange, rock- encrusted, football-sized object. In wonderment, he brings it secretly into the large estate where his mother, Anne (Emily Watson), works as housekeeper and his older sister, Kirstie (Priyanka Xi), also abides.

Soon enough a purplish, lizard-like being hatches. A harshly loud little monster, it bears webbed feet and a horse-like snout and it loves water. Angus names it Crusoe.

Ominously, it begins eating at a startling pace and each good meal causes it to quadruple in size overnight. Keeping it a secret as it crashes through the mansion is tricky.

It will be learned that Celtic legend tells that Crusoe is the latest in an endless succession of a Loch Ness amphibian species of mixed gender that bears just one egg at its life's end.

Complicating matters is that British soldiers are billeted in the house, under the command of Capt. Hamilton (David Morrissey). The official reason for this is that they're to watch for German subs prowling the loch. The men, however, suspect that Hamilton's influential father got him a nice, safe, far-from-the- front assignment.

Regardless, Anne actually is rather taken by this rakish, dashing officer, at least at first.

Meantime, Angus' ally turns out to be the new handyman, Lewis Mowbry (Ben Chaplin), as well as Kirstie, who enthusiastically aid him in maintaining the cover-up of Crusoe.

The personable Mowbry, actually, has a meritorious military record, much to Hamilton's jealousy. Mowbry will vigorously enter the scheme to protect Crusoe from being seen by the British regiment, because he suspects they will immediately turn their cannons on the gargantuan beast if they discover it.

Little Angus is charmingly filled out by director Jay Russell's sensitive perceptions of a 9-year-old's conflicts and urgencies, skillfully avoiding the sentimentalism buttons, even when the boy pines over his daddy, of whose death in the war he is not even aware.

The pompousness and presumptuousness of the military group set up the villain, even as the sympathetic victim, Crusoe, is given a charm and a fearsome quality all at once.

Faltering only a wee bit in a few low-energy scenes between crisis sequences, this is a masterful film that has a fine sense of its balance between old-timey themes and modern special effects. It fine-tunes with a mix of artistry and honesty of technique in just-plain storytelling, which is irresistibly appealing.