Doomsday Creators (The Umbrella Academy) Book Three

After saving the world again, Lucy Hargreeves thought that her and her siblings would get to have a peaceful life. But no.

The siblings return to the present day and find that not everything is as it seems, and they no longer exist in the current timeline.

Lucy is pleased to be home, but her time in the 60's scarred her in many ways, and overcoming trauma was never one of her strong suits. Her siblings are also dealing with their own problems, so there is no one to help her deal with her fragile mental state.

There's also the small issue of the world possibly ending again, as the siblings may or may not have caused another doomsday.