Protect an assassin:
A Client of Mr. Johnson has received Death-threats. There is a big "Gala" (or something along these lines) and he wants protection while he is there. Johnson pays for good clothes, its glamour all over the place, everything is shiny and beautiful, and maybe they actually need to protect him from something.
And then, your PC's lose sight of him for a moment, BOOM, two people drop dead and your Players have to get out of there, before anyone starts to ask risky questions about them.
Mr. Johnson, of course, is absolutely shocked that his Client might have been a "hired assassin" and of course, the players were never meant to feel like a decoy or Knight Errand bait. He would NEVER think about killing i.e. the lawyers trying to bring down the head of the Yakuza, or Journalists which poked a little too deep in the territory of someone.
Because Mr. Johnson is the good Guy. He is as baffled as you are.