Meg and Hawk are part of the FBI's elite K-9 unit. Hawk can sniff out bodies anywhere - living or dead - whether it's tracking a criminal or finding a missing person. When a bomb rips apart a government building on the National Mall in Washington, D.C., it takes all of the team's extensive search-and-rescue training to locate and save the workers and visitors buried beneath the rubble.

When a young girl is found dead in the mountains outside Timber Creek, lifelong resident Officer Mattie Cobb and her partner, K-9 police dog Robo, are assigned to the case that has rocked the small Colorado town. With the help of Cole Walker, a local veterinarian and single father, Mattie and Robo must track down the truth before it claims another victim. But the more Mattie investigates, the more she realizes how many secrets her town holds. And the key may be Cole's daughter, who knows more than she's saying.

Crack CIA analyst Trista Gold is a whiz with the computer, but not so much with people. She hides behind her job, analyzing top-secret code and making recommendations on national security. CIA K-9 officer Sgt. Matt Connors suspects that beneath Trista's uptight appearance, there's a sexy woman itching to cut loose. But he doesn't dare act on his attraction. He's a loner and always will be. Keeping away from Trista is a must-do directive. Until he doesn't have a choice. During a routine assignment, Trista stumbles across a cryptic exchange. Then someone tries to murder her - twice.

It should have been a routine investigation. Instead, DEA K-9 agent Adam "Deck" Decker watches in horror as one Denver hospital seems to be ground zero for overdoses of a new drug. Now Deck can only hope a certain ER doctor will help him and his canine partner track down the source. Dr. Tori Sampson has her reasons for not trusting federal agents, especially ones working for the DEA. But the rash of overdoses—including a heartbreaking case involving a teen—is alarmingly high. And the new opioid is not only extremely dangerous, it defies all the usual medical treatments.

When a fellow FBI agent is kidnapped and a protected witness vanishes, Leo Gallagher will stop at nothing to find them both. So when he discovers a link between the case and a single mother in Wyoming, Leo and his trusty K-9 partner rush to question Alicia Duncan. Could she be the key to locating the missing persons?