Blue Bloods Season 13 Episode 9 revolves around Joe Hill's feelings about the father he never knew.

When Frank discovers that someone has knocked over Joe Reagan's gravestone, Joe Hill insists on investigating. Frank doesn't want him to, but Joe does anyway.

The two butt heads several times, culminating in Joe mentioning it at Sunday dinner, which shocks everyone because Frank never told any of them about the desecration of Joe's grave. All the other Reagans would have helped Joe Hill find the SOB who did it if they knew anything about it. Joe leaves.

Frank talks to Joe's mother and gets some advice about how to connect with this grandson he never knew.

Meanwhile, Danny tries to help an old partner. His partner's wife, Naomi, comes to him. Her husband is undercover and is drinking and using and never comes home. John is consistently defiant when Danny tries to intervene, but when the bad guys kidnap Naomi, John needs Danny to help get her back.

Finally, Eddie is resentful when her boss steals a case involving stolen puppies out from under her and Henry is determined to catch the scammers that stole $6,000 from his friend.

To find out what happens, watch Blue Bloods Season 13 Episode 9 online.