The stalker problem in Hollywood has gotten so bad, that celebs are now having to hire PIs to track down these people to make sure they stay away ... including a famous violinist.
We did a ride-along with a seasoned vet in this industry -- a private investigator named Joe Dalu ... who was recently contracted by Lindsey Stirling to locate a man she claims has been stalking her and making her life a living hell.
Check out how Dalu explains this phenomenon to us in the car -- he says there are a lot of law enforcement agencies these days that don't want to serve stalkers with stay-away orders, out of fear of being attacked and harmed ... and as a result, there's no one left to do it.
That's where Joe comes in ... and you can see him doing the job here -- confronting a man who's alleged to be obsessed with Lindsey.
BTW, this guy has ties to hounding Taylor Swift too -- he's been obsessed with her for more than a year -- which just speaks to the larger issue.
Anyway, the entire interaction here is part of a show airing Monday on FOX called 'TMZ Investigates: Obsessed and Dangerous: Hollywood’s Stalker Crisis' -- kicking off a new series that'll start to air weekly. The show starts at 9/8c ... and you won't wanna miss this.