Unknown Threat

series: Defend and Protect

Cover Art

Where to Purchase

More Options


"Do. Not. Miss. This. One!"--Ronie Kendig, bestselling and award-winning author of The Tox Files

US Secret Service Special Agent Luke Powell is lucky to be alive. Three of his fellow agents have died in unusual circumstances in the past ten weeks. Luke is devastated by the loss of his friends and colleagues, and his inability to locate the killer feels like a personal failure. He and his team are experts at shielding others, but now the protectors are in need of protection.

FBI Special Agent Faith Malone is driven to succeed and confident in her ability to solve every case she's assigned. She's been put in charge of the investigation into the unprecedented attacks, and with Luke's life in danger, the stakes have never been higher. But it's hard to know how to fight back when you don't know who the enemy is.

Luke has teamed up with Faith before, but he's not convinced she's up for the job and she's not convinced he's telling her everything he knows. As more agents are targeted, Luke and Faith will have to learn to trust each other and work together to bring a killer to justice and prevent any more names from joining their fallen brothers and sisters on the Secret Service Wall of Honor.

"Lynn H. Blackburn is an amazing voice in romantic suspense--don't miss her!"--Lynette Eason, bestselling author of Danger Never Sleeps series

"Unknown Threat is a fantastic read!"--Elizabeth Goddard, award-winning author of the Uncommon Justice series

"Lynn Blackburn has created a page-turning novel with all the elements I've come to love in her books."--Cara Putman, award-winning author of Flight Risk and Imperfect Justice 

Lynn H. Blackburn is the author of Beneath the Surface, In Too Deep, One Final Breath, Hidden Legacy, and Covert Justice. Her books have won the Carol Award, the Selah Award, and the Faith, Hope, and Love Reader's Choice Award. She lives in Simpsonville, South Carolina, with her true love, Brian, and their three children.


"Blackburn's Defend and Protect series is off with a bang in Unknown Threat. This heart-racing romantic suspense is one for the keeper shelf! Don your tactical vests and get ready to engage a compelling story that will forbid you from abandoning its pages. Do. Not. Miss. This. One!"

Ronie Kendig, bestselling, award-winning author of The Tox Files

"Unknown Threat is a fantastic read! An action-packed opening and sharply drawn characters drew me right in and held me captive. Blackburn has an exceptional gift for weaving twisting plots with characters that walk right off the page. I absolutely adore Faith, the bright and stalwart FBI special agent. I love the attention to detail regarding Secret Service operations. The swoon-worthy romance between Faith and Luke is the perfect slow burn. Unknown Threat is an exciting start to a thrilling new romantic-suspense series!"

Elizabeth Goddard, award-winning author of the Uncommon Justice series

"In Unknown Threat, Lynn Blackburn has created a page-turning novel with all the elements I've come to love in her books. The hero and heroine are unique and compelling, while surrounded by a rich cast that adds depth to the story. The suspense thread is intense and pulses with energy and pressure. And the romance? It's perfection, with tension to keep me rooting for the characters. It's a perfect read for those who love engaging stories that are threaded with hope."

Cara Putman, award-winning author of Flight Risk and Imperfect Justice

The Author

  1. Lynn H. Blackburn
    Lynette Eason

    Lynn H. Blackburn

    Lynn H. Blackburn is the award-winning author of Never Fall Again, as well as the Dive Team Investigations and Defend and Protect series. She loves writing swoon-worthy Southern suspense because her childhood fantasy was to become a spy, but...

    Continue reading about Lynn H. Blackburn


"By far the best romantic suspense book I have read this year! Fans of Blackburn will not want to miss this fantastic read!"


"Unknown Threat by Lynn H. Blackburn is a fast-paced romantic suspense read. I loved the action-packed scenes."

Urban Lit Magazine

"Wow, talk about an intense and riveting read. This series started with a bang and kept up a thrilling pace. I think this is my favorite book by Blackburn to date."

Relz Reviewz



Book Trailer