Aquarius

...and that's okay! There's a serial-killer cult-leader who has dirt on various officials, a follower who has reservations, a down-and-dirty ethically-challenged cop teamed with an idealistic partner with a scandalous (for the time period) secret, all mixed with classic music and drenched in sepia.

The acting is reasonable (not great, but not horrible... especially for network television) with some good portrayals by serial-killer Manson (Gethin Anthony) and good-cop Damon (Brian Shafe), and the sub-plots give a good sense of place (civil rights issues, drugs, sexuality).

The beginning is a bit slow, but you would expect that (it's not the type of show where you'd jump straight into a manhunt or anything). It's probably a bit more on the character drama- side than the action-side, so keep that in mind.

In the continuum of shows out there I'd rather watch this than The Americans, but I'd throw Aquarius under the bus for Hell on Wheels.