The Name of the Star by Maureen Johnson

Rory Deveaux arrives in London during a very exciting time. It will soon be the anniversary of the Jack the Ripper killings. In 1888, a person who police nicknamed Jack the Ripper killed a number of women in London, England, in a short period of time. The killings stopped, but "Jack" was never caught.

Now, each year on the anniversary of the killings, London is filled with  a sort of party atmosphere. Stores are selling Jack the Ripper tee-shirts and pubs are packed with people.

Until a murder occurs. The murder is caught on a surveillance camera, but no killer can be seen ...except by Rory.

If you like murder mysteries and ghost stories, you will love this book.