Who is Jonathan Landers/Jack from Hourglass and what is their importance?

Jonathan Landers is the novel's antagonist. He is second in charge at Hourglass, and therefore becomes the head of Hourglass when Liam Ballard is killed. Jonathan is jealous of those who can travel through time, and he has been searching for a way to do it himself, using the gifts of those who come to Hourglass for help. At the end of the novel, Michael and Emerson learn that Cat has been helping Landers travel through time with the use of a formula Liam developed to give those without the time traveling gene the ability to travel through time. When Emerson sees Landers the night of Liam's death, she recognizes him as Jack, a rip that she has been seeing in her home.