Sudden superpowers create and then solve problems for two children in these breezy imports, re-issued on this side of the water in a single, dos-a-dos volume. Shortly after eight-year-old Josie begins bending iron bars, lifting cars and accomplishing other astounding feats, she and her family fall into contract slavery to an unscrupulous hustler who forces her to use her strength for money rather than good. On the flip-side, when his parents disappear on the way back from a Moon vacation, Sam is abducted by evil neighbor Hilda Hardbottom, but manages to hold his own thanks to Splodge, a small alien wayfarer who gives him a shot of invisibility. Though Sam has a mischievous streak, both children are goodhearted sorts, averse to abusing their gifts, and Gardner brings both stories around to happy endings. The author adds amusing ink sketches to nearly every page, heightening the appeal for less-practiced readers. (Fantasy. 9-11)