Numb3rs Fanfic Finders

I'm looking for a fic which had Don and Colby in a BDSM club as part of a sting op. Don was the Dom, Colby the sub. Somewhere along the way Don realizes that Colby isn't just playing a part, and at the end they get together. IIRC the guy they're after tries to get Colby alone and assault him but Don appears before anything bad happens. 

Does anyone recognize this? I loved it when I first read it and would really like to find it again.