HAZMAT HEEL-AND-TOEThe message came over the CB in good-ol’-boy code. “Death on Truckers just joined the party on Interstate seven-eight,” the invisible driver drawled, and FBI Agent Dawna Shepherd clicked her seatbelt into the latch. Her cellphone chimed. “That’ll be Chambers,” she said to her driver, Joe Menasria. With one hand, Dawna pressed her cellphone to her ear. With the other, she braced herself for the jolt she knew would follow when their liquid cargo shifted. Across the doghouse from her, Joe released the trailer brakes with a whoosh of air, shifted out of neutral, and moved the chemical tanker across the truck stop lot toward the on-ramp. “Heard it on the CB,” Dawna reported to Benjamin Chambers, her Bureau colleague. Chambers and another agent had been at the I-78 rest are

