Angels Unlimited is the title of a series of novels written for young adults by Annie Dalton. The books are based around Melanie Beeby, who is killed in a traffic accident on the day after her thirteenth birthday. She then finds herself transported to Heaven. The Heaven of this universe is a lively and vibrant city, populated both by dead humans-turned-angels and Heaven-born beings known as pure angels. This city is also where the headquarters of the Agency are situated. The Agency is an elite group whose job is to counter the Opposition, informally known as the PO Ds or Powers Of Darkness - the polar opposite of the Agency.