This episode opens with the NCIS: OSP team in Los Angeles tracking a Marine meeting with an arms dealer. Said Marine slips their surveillance and, after the credits, turns up dead in D.C. Gibbs and McGee go to L.A. to aid OSP's investigation, while Tony concerns himself with Ziva's strange behavior the past two days.
I'm not sure what to make of Part One. It wasn't as different from NCIS as NCIS was from JAG. We meet the new cast, two of whom have history with Gibbs, but neither history is explained in much detail. Part Two will supposedly go into that.
The transition from JAG to NCIS was helped by the recognizability of Mark Harmon and David McCallum. OSP has LL Cool J and Chris O'Donnell, but neither has had time to really distinguish himself. More next week.