There are some characters who you gradually get to like. Others enter the cool department from the get-go.
I'll get to that in a second.
There are two broad plot-lines running through this. The first is the conclusion (sorta) of the plot of last season and the resolution of the cliff-hanger ending of Season 6.
Basically, a serial killer was holding the baby of the NY crime lab's resident whipping-people, Danny and Lindsay Messer hostage, while pointing a gun at the former. We heard a gunshot over the closing credits.
In what is somewhat of a cheat on the cliffhanger resolution (adding bits to a time gap that only appeared to be a few seconds), Lindsay demonstrated that it really isn't a good idea to threaten the baby of an NYPD cop and after some initial trepidation, shot the serial killer in the chest. (The full Mozambique drill might have been deemed as a bit excessive).
Cut to five months later. Mrs. Messer, wearing a uniform with a cap that is a size too big for her, receives a Combat Cross placed around her neck by Mac, who isn't wearing a uniform. Lindsay isn't too happy about this, feeling that she was merely doing her job. After a counselling session, she chucks her medal in the bin. Eventually, she is persuaded by Mac and Danny that she deserves the medal, which Danny gives back to her (I hope he cleaned it first). My two cents on this - doing your job generally involves a tactical vest and back-up, not a stand-off in your pyjamas. There's a thing called going beyond the call of duty.
This is arguably the weaker of the two plotlines. While I like Lindsay (who has got a fair amount of flak over the years), this wasn't the best episode she's been in.
However, this emotional plot-line was far more than made up for by the main criminal investigation one. While the team are all watching Lindsay get her medal, a new character (who didn't get the memo) arrives at the empty lab... and finds a dead body.
The new character, Josephine "Jo" Danville, a former FBI agent from Virginia, is a far better character than Stella Bonasera and her consistently low-cut tops. She hits the ground running, making quips, memorably psyching out lab tech Adam with some good guesses about his social habits (which seem to involve porn) and playing a key role in solving the case. I have a new favourite character in CSI:NY.
This very strong opener ends with a stand-off at the Chrysler Building and I'll just note that the show seems to be trying to kill people at every major NYC landmark before wrapping this up.
4/5. The show stays in a very good second place in the CSI league.
Edit 16/1: It's Jo Danville, not Jo Ward. Selina Ward is the actor who plays Jo Danville...