Ava Glass started every London weekday the same way. In the entrance to her office building, she would place her belongings on an airport-style conveyor belt to be x-rayed. Then she’d enter one of ten pods. She would scan her ID card, step inside, and the doors on either side of her would shut. For those few seconds, it was just her and her thoughts in the “glass coffin.” “We all used to talk about it,” she said. “What goes on? Was it sniffing for explosives?” These were a few of the lighter questions native Texan Glass had about her early-aughts job: working with counterterrorism spies for the British government.Those daily security measures are vividly re-created in Glass’s latest novel, The Trap (September 3, Penguin…