This one came a little out of left field for me - it was only right at the end when I "got" the link from previous books.
Penny is a physical therapist who lives next door to Joe, an LT in the SEALs. Joe is the sole survivor of a terrible tragedy in Afghanistan where somewhere in the region of 20 soldiers died.
Joe has led a charmed life, he has a string of girlfriends that he entertains in his hot-tub.
Badly injured after the accident Joe blames himself for the tragedy - was he trying to relive his glory days by leading the team? Penny has always had a bit of a crush on her playboy neighbour but she is also a deeply kind and caring woman. Penny has to step in on a couple of occassions to help when Joe's self-destructive behaviour becomes an issue.
And, of course, she is his physical therapist.
The plot was pretty fanciful - I don't believe that ricin could go missing for five years and the FBI just shrug its shoulders - I suspect they would also have investigated the subsequent death of anyone who had been closely connected with the ricin before it disappeared.
The plot featured more heavily than in the three previous books - although the perpetrator was obvious from the second s/he was introduced into the plot. I also question the reason why the perpetrator was targetting the girls - but who cares?
One of the things I like with this series so far is that the female protagonists are strong, resourceful women who, by and large, rescue themselves. Strangely, that can not be said for the secondary romances - which, to be honest, I heartily dislike. In the previous book and this one (or was it the second book and this one?) there is a secondary romance in which the male acts like a bit of an alpha a*hole. Maybe it's because I'm a contrary bitch but if a man I had barely met started to tell me what I would and wouldn't do, or tried to tell me my "issues" he'd get a verbal smackdown. These secondary male characters ride rough-shod over the women, not taking no for an answer, ignoring their stated desires etc. I know it's meant to be shown as nurturing and caring but it's like a red rag to a bull.
Anyway, this series continues to loosely connect the stories whilst avoiding the formulaic issues affecting similar series.