Glance at Emma Howe, and what you see is a no-nonsense 50-year-old built to mow down walls. Widen the perspective to include her brand-new associate, Billie August, and you might decide you’re viewing Emma’s exact opposite. But you’d be wrong. In the ways that count, you’re looking at a matched pair. True, Billie hasn’t hit 30 yet. Nor is there anything tanklike about her. She’s slender, blond, beautiful, with an elegance that suggests to Emma (audible snarl here) that “she wore white gloves in her soul.” The fact is, though, that there’s as much steel and drive in Billie as in Emma, and, truly making them sisters under the skin, as much rampaging curiosity. Emma hires Billie out of necessity. Her p.i. is short-handed, and now there’s a case involving a missing 18-year-old girl that desperately needs attention. Eventually, the investigation will uncover a murder, connect to an earlier one, and, almost incidentally, to a child porno ring. But the fun here is all in the ripening of an unlikely relationship. As triumphs mount, Billie stops being afraid of her formidable boss, and Emma begins to understand how lucky she is. A departure for Roberts, who forsakes her frothy (Philadelphia-based) Amanda Pepper series (The Mummers’ Curse, 1996, etc.) for the opposite coast—and something darker and richer. The Howe-August series could be one to watch.