To my friend Bess, the major Hollywood production coming to River Heights is her chance for fame as an extra. To me it's a chance to get involved in a big mystery. Looks like the drama on this set really kicks up when the camera's not rolling. <P> Since Chief McGinnis wanted to hire a "professional" (in other words, not me) to look into the problems that have been plaguing this production, I'll be working undercover as a stand-in. I have no idea who this detective will be, and fortunately, I'm not in this for the credit. But I am determined to crack this case faster than any professional can say "Cut!"