One of the most powerful images in American history is of a slave who escaped a Mississippi plantation during the last days of the Civil War and found refuge with Union soldiers in Louisiana. The stark photo, with the man’s back a mess of gnarled scars, was a crucial tool in showing the evils of slavery and supporting Abolitionists’ cause. There’s a powerful story to be told about that photo and the power of images to illuminate truth. Unfortunately, Antoine Fuqua’s Emancipation is more interested in having Will Smith fight alligators.

Smith plays Peter, a slave ripped away from his wife and daughter to help build a railroad for the Confederates. When he hears that Lincoln has emancipated slaves, he makes a daring escape through the Louisiana swamps to try and reach Union troops and urge them to rescue his family.

Fuqua, director of action thrillers like...