I can't help with any practical advice Ka26, but it reads like an idea for a book!
A perfectly ordinary looking pick up from a wealthy residence turns out to be the kidnap of a beautiful heiress. The pilot is duped into going along with the plan, but when things go wrong he uses his skills (and helicopter) to rescue the young woman. Death defying new slant on the old car chase gag - helicopters chasing through tunnels .........
Oh, wait, its been done.
Roger.