The War that Saved My Life by Kimberly Brubaker Bradley

I waited for a reply.
Twice a day the postman dropped letters through the slot on the front door.
Twice a day I went to look. Susan said it would take at least two days for the
letter to get to London, and two days for an answer to come back to us, but
ten days passed and still there was nothing.
“I bet they aren’t delivering letters in London,” Jamie said. “Because of the
war.” I could tell by the look on Susan’s face she didn’t think that was true.
On the twelfth day a letter I recognized fell at my feet. My own. Return to
sender was scrawled across it. No longer at this address.
“She’s moved,” Susan said, turning the unopened envelope over in her
hands. “She lives somewhere else now.”
Susan said perhaps Mam had a new job and had moved to be closer to it.
She said perhaps the government had requisitioned our flat. She said there
were a number of reasons that Mam might have moved that didn’t mean she’d
abandoned us, and she, Susan, would make inquiries through the WVS.
Someone in London was bound to know where Mam had gone.
“What happens to us?” Jamie asked, wide-eyed.
“You stay with me,” Susan said, “just like you do now. Your mam knows
where you are. She knows you’re safe.”
“What happens when the war’s over?”
Susan took a deep breath. “Your mam will come and get you.”
“What if she doesn’t?” Jamie insisted.
“Don’t worry,” Susan said. “I’ll make sure someone always takes care of
you.”
“I’ll take care of him,” I said, suddenly furious. “I took care of him before,
not Mam.” I hated—I hated—oh. Even in my head I still couldn’t say I hated
Mam. Even now. If I could get my foot fixed, maybe she’d be different.
Maybe she’d love me. Maybe she would.
“You did a good job taking care of Jamie,” Susan said. “But it was a big
job, and you shouldn’t have had to do it. So now you can relax. I can take
care of you. You don’t have to fight so hard.”