Doctor Who at Childhoods End

"Past, present and future collide as the thirteenth Doctor meets classic Doctor Who companion Ace in the first epic novel from the woman who played her, Sophie Aldred. Once, a girl called Ace traveled the universe with the Doctor, until in the wake of a terrible tragedy they parted company. Decades later, known as Dorothy McShane, she is the reclusive millionaire philanthropist who heads A Charitable Earth. Yet she is haunted by terrible nightmares, vivid dreams that begin just as scores of young runaways are vanishing from the dark alleyways of London. Elsewhere, investigating an aline satellite orbiting the Moon with Ryan, Graham, and Yaz, the Doctor is thrown together with Ace once more. Together they must unravel a plot that will cost thousands of lives. But can the Doctor atone for her past incarnation's behavior, and what must Ace sacrifice to achieve victory for herself?"