Adrienne Wendell was once an exceptional ultramarathoner, a runner whose times were within striking distance of setting records. Years ago, she gave it all up when her son Ethan was hit by a car while she was in a race and unable to come to his help. He survived, but it horrified her that she had not been around to help. There was another reason she put running behind her: she had leveled a career-ending accusation at one of the world's most celebrated coaches--just before he mysteriously died. She instantly became a pariah in the running community.

Now seven years have passed, and Adri is back on her feet. She's headed to Morocco for a staggering 250-mile race through the Sahara Desert organized by none other than Boones--a race director so mysterious and elusive he only goes by one name. Boones's races are famously sadistic. Routes can change moments before the starting gun fires, and inevitably there are bizarre challenges that test the runners' will and stamina. Adri is here to prove that, despite everything that has happened, she can still do it. But she's also here for answers to the mysteries that cloud her past, and she's as determined to find them as she is to finish the race. The only question is who is trying to stop her.

There are secrets swirling in the hot desert sands, and as Adri gets closer to the explosive truth, the danger climbs with every step she takes.