Found: Kids Fantasy magical chapter book series 2012 or earlier

Girl goes to a hotel for a job to find her missing sister and finds out she's locked behind a magical moving staircase that leads to a tower. It's a series and this is the one I remember the plot of. It's a kids book and has a evil guy keeping her captive.

Sounds vaguely like Conrad's Fate, from the Chrestomanci series by Diana Wynne Jones, although the main character in that book is a boy. To trace the trapped girl, he gets a job as part of the domestic staff in a grand mansion.

>2 konallis: that's it! Thx so much I've been looking for this book for 3 years

>3 bales1997: Great! I wasn't sure if it was too different from your description, but the enchanted staircase was a distinctive enough detail to be worth a try.