“A working-class wizard and his assistant help a girl rescue her friend who is being held captive by a voodoo priestess during Mardi Gras in New Orleans.”

I like this one better than your other one. This one is more descriptive. Nice.

Dig it!
The damsel in distress and needing a rescue appears to be a friend of a friend, so I wrote up an example of her being more prominent – make this your own.

Example:
“A working-class wizard and his apprentice set out during Mardi Gras to rescue the mayor held captive by a New Orleans voodoo priestess.”

Hope this helps, take care.