Investigator is another new profession that came in with the Ambitions expansion pack.  My Investigator Sim is only at level 5 so far, but one thing I can say for sure: this profession will keep you (the player) hopping!

This is one of the professions with no set hours, which I find easier to play.  There are several ways to advance - by going on stakeouts, solving mysteries, and improving your Logic skill.  Stakeouts are boring, but they work well if you need something to keep your Sim busy while you eat dinner.  Just click on the ground on any public lot, and choose "Stakeout."  Your Sim will change into their Investigator outfit (a fedora and a tan trench coat) and stand around holding bits of shrubbery in front of their face to "hide."  

Eventually they decide they've seen enough.  When your Sim calls it quits, the next step is to write a report.  Click on a computer (either their own or one of the public terminals at the library) and choose Investigator -> Write Report.  This takes a little while too, so you can finish up that grilled cheese sandwich and put your plate away.

(The only confusing thing about the stakeout is that at one point I got a message from the game that my Sim wished she could afford a van for stakeouts.  I bought her the van in Buy Mode, but I don't see any way to use it.  No idea what that was about.)

For the most part, your Sim will be solving crimes.  This is only a little more complicated than clicking "Next" when you play a Facebook game.  If you don't have a current crime, you only have to wait a little while before someone gives you a call.  If you're impatient you can have your Sim use the computer to find a new crime to solve.

Solving crimes means following a chain of actions, none of which are particularly complicated.  You may have to interview three random Sims - just click on the Sims and choose the yellow "Interview" option.  Or you may have to snoop through someone's mail - just click on their mailbox and choose "Snoop."  You get the picture.  The game really holds your hand through these steps.  And funnily enough, the people you need to talk to are always available, day or night.  

If you get tired of sending your Sim back and forth across town chasing down leads or whatever, you can have them "do low-level paperwork for the police."  Just click on the police station and your Sim will vanish down that rabbit hole, just as if they really worked there.  You even get to choose from the available work options like "Meet Other Cops" or "Suck Up To Boss."

You don't get paid a terribly large amount as an Investigator.  But you do get two cool things you can actually display: a cool film noir-style door with a frosted glass window, and the "Investigator's Case Board" (pictured above) which is kind of a neat decoration.