Tunnel of Bones

Trouble is haunting Cassidy Blake . . . even more than usual.

She (plus her ghost best friend, Jacob, of course) are in Paris,
where Cass's parents are filming their TV show about the world's
most haunted cities. Sure, it's fun eating croissants and seeing
the Eiffel Tower, but there's true ghostly danger lurking beneath
Paris, in the creepy underground Catacombs.

When Cass accidentally awakens a frighteningly strong spirit, she
must rely on her still-growing skills as a ghosthunter -- and turn
to friends both old and new to help her unravel a mystery. But
time is running out, and the spirit is only growing stronger.

And if Cass fails, the force she's unleashed could haunt the city
forever.

New York Times bestselling author Victoria Schwab returns to the
spooky and heart-pounding world of City of Ghosts, delivering thrilling
new adventures and an unforgettable spin on friendship. (Because
sometimes, even psychic ghost best friends have secrets...)