The Natchez Trace National Parkway stretches 444 miles from Nashville to Natchez, the oldest town on the Mississippi River. It's the perfect road for a relaxed pleasure drive. Unfortunately for park ranger Luke Fereday, lately it's being used to move drugs. Sent to Natchez to infiltrate the organization at the center of the drug ring, Luke arrives too late to a stakeout and discovers the body of his friend, park ranger John Danvers.

When one Coast Guard officer is found dead and another goes missing, Coast Guard Investigative Service special agent Finn Walker faces his most dangerous crime yet. His only clues are what little evidence remains aboard the dead officer's boat, and the direction the clues point to will test Finn and the Guard to their limits. When investigative reporter - and Finn's boss's sister - Gabby Rowley arrives, her unrelenting questions complicate an already volatile situation. Now that she's back, the tug on Finn's heart is strong.

EMS helicopter pilot Penny Carlton is used to high stress situations, but being forced to land on a mountain in a raging storm with a critical patient - and a serial killer on the loose - tests her skills and her nerve to the limit. She survives with FBI Special Agent Holt Satterfield's help. But she's not out of the woods yet.

US Marshals Madison James and Jonas Quinn are thrust into a high-profile case when they are called on to transport two prisoners across the country on a private plane. But when the plane experiences engine trouble en route from the Pacific Northwest to Colorado, the pilots crash-land the aircraft deep in the heart of the sprawling Salmon-Challis National Forest. When Madison and Jonas regain consciousness, they find both pilots and one prisoner dead - and one fugitive on the run. 

Former pararescue jumper Orion Starr is haunted by the memory of a rescue gone wrong. He may be living alone in Alaska now, but the pain of his failure - and his injuries - has followed him there from Afghanistan. He has no desire to join Hamilton Jones' elite rescue team, but he also can't shirk his duty when the call comes in to rescue three lost climbers on Denali. Former CIA profiler and psychiatrist Jenny Calhoun's yearly extreme challenge with her best friends is her only escape from the guilt that has sunk its claws into her.