Necropolis is the Fourth Book in the series of The Power of Five. It features the introduction of the fifth gatekeeper - Scarlett Adams.
Scarlett Adams is of Chinese origin but, like all other gatekeepers, her parents seem to have died after she was born. This lead to her begin adopted by a british family and her having been raised in England. It is later revealed that her parents are hardly ever around and have had a divorce.
Scarlett is bought to China as her dad is living there, because of his job.
Little is known of Scarlett Adam's powers, except they seem to be weather oriented. She seems to be able to predict the weather and even change it.
In the book, she is even able to form a hurricane.