When a mystery novel really grips us, as Scott Turow’s Presumed Innocent did in 1987, the inevitable movie version rarely turns out the way we imagined. Turow, a successful Chicago lawyer, crafted a first novel that was equal parts whodunit, courtroom drama, warped love story and insightful take on the limits of the legal system. I pictured William Hurt as Rusty Sabich, the prosecuting attorney who cheats on his wife, Barbara (I envisioned Barbara Hershey), with his ambitious, sexually avid colleague, Carolyn Polhemus (to my mind, a perfect role for Ellen Barkin), and ends up on trial for Polhemus’s murder. Instead, the studio cast Harrison Ford as Rusty, Bonnie Bedelia as Barbara and Greta Scacchi as Carolyn. No hard feelings. All do impressive work, and Ford — breaking again from his Indiana Jones heroics — is astonishingly fine in a performance of controlled intensity. Raul Julia is a marvel as Rusty’s wily lawyer, Sandy Stern (the protagonist of Turow’s current bestseller, The Burden of Proof). What’s harder to adjust to is the measured pace of director and co-writer Alan J. Pakula (All the President’s Men, Sophie’s Choice). Turow’s book was electrifying; Pakula’s screen version pulls us in slowly and cuts less deeply. But the spellbinding power of the tale still takes hold. If you haven’t read the novel, the climax may floor you. Even readers with reservations about the ways the film fails to measure up to the book should appreciate a smart, passionate, steadily engrossing thriller in a summer of mindless zap.