The true story of John Knapp, a hapless cabdriver wrongly sent to death row after a suspicious fire killed his two daughters. On a cold morning in November 1973, a fire broke out in a bedroom in the tiny Knapp house in East Mesa, Ariz. Iona, four and a half years old, and Linda Louise, three and a half, died within minutes. The mess inside made it difficult to determine the cause of the fire, and initially the blaze was ruled accidental. But within two weeks the authorities had changed their minds, and John Knapp, 27, was charged with murder. His wife, Linda, fled the state. Poor, ill, and uneducated, Knapp confessed to the crime, and though the evidence was weak--the children played with matches, and the house was unheated--the state asked for the death penalty. Parloff, a senior reporter at American Lawyer, notes the horrifying inadequacies of Knapp's defense: His lawyers were grossly underfunded, and one, Charles Diettrich, became a full-blown alcoholic in the midst of the trial. After Knapp's conviction, Diettrich handled the appeal, and missed deadlines and court dates until Knapp was sentenced to die in ther gas chamber. The case eventually made its way to a Phoenix firm whose lawyers became passionately convinced of Knapp's innocence. Using the concept of ``flashover'' (a term referring to the time it takes for gases in a fire to expand enough to ignite everything in sight), they were able to demonstrate scientifically that Knapp did not kill his children. (The actual cause of the fire was never determined.) Parloff covers the trials in such minute detail that some of the text will seem inscrutable to lay readers; the legal footnotes are impenetrable. Knapp's story is dreadful, but the narrative conspires to make it dull. Though written like a brief, this is nonetheless an intriguing behind-the-scenes look at the slow machinations of the legal system.