Talk about starting with a bang. While retired and widowed lawyer Martha Patterson is still being warned against ``the Mother Teresa syndrome'' in her new job at West Brooklyn Legal Services, one of the paralegals bursts into the office bleeding from a head wound; he's been mugged, says Carlos Quinones, by three men who stole the rent-strike money he'd just collected from The Building. Hours later, just after Martha gets off the phone with Tessie Doone, a tenant of The Building whose Social Security checks have stopped coming, crazy Wilma Oberfell stalks into the office claiming ``I don't know whom I can trust'' before following Martha home, then skulking away. And the next day, when Martha goes out to The Building to talk to Tessie, she runs into Wilma again, strangled by a convenient burglar. Even if you don't believe the burglar story, the suspects--the decamped tenants' association treasurer at The Building, Tessie's fast-talking grandson Kareem Hewitt, a mysterious man on The Building's fire escape, and of course all those lawyers at Brooklyn Legal Services--are almost too plentiful to believe. Sprague follows her Edgar-winning YA novel, Signpost to Terror (1967), with a mazelike tale that not only features an unobtrusively gifted detective--Martha's eye for detail puts her head and shoulders above most of her big-ticket competition--but provides a virtual handbook of rarely fictionalized pro bono legal maneuvers.