The Navigator Trilogy Series by Eoin McNamee

Owen turned to Cat but she was staring into the woods, her face a mast of fear. Far off, but moving closer, were two figures, both white, both faceless, seeming to glide between the trees. "The Harsh" whispered Cati."They're here."" One day the world around Owen shifts oddly: Time flows backwards, and the world and family he knew disappear. Time can only be set right when the Resisters vanquish their ancient enemies, the Harsh... moreOwen turned to Cat but she was staring into the woods, her face a mast of fear. Far off, but moving closer, were two figures, both white, both faceless, seeming to glide between the trees. "The Harsh" whispered Cati."They're here."" One day the world around Owen shifts oddly: Time flows backwards, and the world and family he knew disappear. Time can only be set right when the Resisters vanquish their ancient enemies, the Harsh. Unless they are stopped, everything Owen knows will vanish as if it has never been...And Owen discovers he has a terrifying role to play in this battle: he is the Navigator. "From the Hardcover edition. less

CATI, THE BOLD Watcher readers met in The Navigator, returns from the shadows of time to summon Owen and Dr. Diamond, for time is literally running out. The moon is coming closer to the earth, causing havoc with weather, tides, and other natural cycles; people fear the world will end. To discover what’s gone wrong, Cati, Owen, and the Doctor must take an astonishing journey to the City of Time, where time is bought and sold... moreCATI, THE BOLD Watcher readers met in The Navigator, returns from the shadows of time to summon Owen and Dr. Diamond, for time is literally running out. The moon is coming closer to the earth, causing havoc with weather, tides, and other natural cycles; people fear the world will end. To discover what’s gone wrong, Cati, Owen, and the Doctor must take an astonishing journey to the City of Time, where time is bought and sold. There, Owen begins to understand his great responsibility and power as the Navigator. less

"The final book in the thrilling Navigator trilogy." Twice the Harsh have tried to destroy time, and twice Owen and the Resisters have banded together to stop them. In "City of Time, "Owen killed the Harsh king, and now the Harsh are hungry for revenge. Their massive fleet is ready to set sail on the sea of time and hunt down the wily Navigator. In this third and final adventure, the Navigator and his friends use every last ounce of bravery and endurance to fight the toughest battle ever... more"The final book in the thrilling Navigator trilogy." Twice the Harsh have tried to destroy time, and twice Owen and the Resisters have banded together to stop them. In "City of Time, "Owen killed the Harsh king, and now the Harsh are hungry for revenge. Their massive fleet is ready to set sail on the sea of time and hunt down the wily Navigator. In this third and final adventure, the Navigator and his friends use every last ounce of bravery and endurance to fight the toughest battle ever. As Owen searches for a solution, he travels through time to meet his father and grandfather, and discovers that the mysterious Frost Child holds the key to the power of the Harsh. less