I give the episode a passing grade because it was very INTERESTING to follow for 95% of the time -- the murder cases and the Ducky romance. Also, nice friendly team interactions. Tony was competent as usual, but I am getting tired of his non-stop drivel about movie references and everything else under the sun; everything he says is an often tired attempt at humor. Cheryl Ladd was well cast.
***Spoilers**** I suspected that Mary was involved with the murders in some way because they gave her and Ducky so much screen time that, pleasant as it was, seemed kind of unnecessary otherwise. I couldn't believe my eyes and ears when the revelation came and they gave that terrible, crazy, stupid reason for her actions: a supposedly normal woman with a high position in the social health field and many colleagues, suddenly becomes an elaborate serial killer just to create an interesting case/challenge for her NEW Chief Medical Examiner/ Forensic Psychologist boyfriend!
I thought there were plot holes, especially there being no real good reason for a dozen NCIS agents to traipse through the woods looking for WHAT, WHERE, WHY? I won't take up the space to explain that.
Still, the preceding 95% was fun and perked my interest.