The Reagan Sunday dinner is a time to celebrate being together as a family, but for 13 years, there's been an empty seat at the table.

Joe Reagan passed away in the line of duty, but his memory is never far from Frank's mind, especially now that the son no one knew Joe had is part of the Reagans' lives.

And on Blue Bloods Season 13 Episode 9, Joe's memory comes up in a special way when Frank and Joe Hill set out to rectify a grievous insult.

This promises to be one of the most emotional episodes in Blue Bloods history. Frank has never gotten over the loss of his son, and Joe Hill never knew his father.

Visiting Joe Reagan's grave will be emotional for both men, especially because they're on a mission to protect his memory.

What kind of insult could they be dealing with?

We know that Joe Reagan died in the line of duty and that he had been investigating a secret society of dirty cops. Could someone have suggested that Joe was dirty too?

Joe Hill works undercover, and Jamie works top-secret cases involving potentially compromised police officers, so it's possible one or both of them could uncover something unsavory about Joe Reagan.

Joe Hill's mother will appear, so she might also have information Frank would rather not hear.

Frank and Joe Hill will likely bond as grandfather and grandson as they work to restore their late relative's reputation. Frank may have plenty of stories to tell about his late son, and his grandson will be eager to learn more.

The two assume there's been an insult to Joe Reagan's memory, but what if it turns out he wasn't as clean as they think?

Suppose it turns out that Joe Reagan did something underhanded that nobody knew about. That could be even more emotional, especially since he isn't here to explain himself to his family.

That could leave Frank and Joe confused and saddened and open the door for serious drama.

These two aren't the only ones taking a trip down memory lane. Danny and Baez will investigate a case involving a former partner of Danny's who has now spiraled out of control.

Will this person be a new character, or will Jennifer Esposito make a guest appearance?

According to spoilers, Danny will have to intervene in an undercover assignment. What could be so problematic that he's called in on this one?

Danny could struggle to control his temper or biases depending on what's going on and who's involved. Baez may need to help rein him in before he does something he regrets.

If Danny's former partner is in bad shape mentally or emotionally, that could be heartbreaking. It's always painful to witness someone you care about spiral out of control, especially if their problems interfere with their competence or change their personality.

Erin and Henry will also work together, which should be fun.

Henry is at his best when he's doing whatever police work he's still able to do, and this time he's perfectly poised to catch the bad guys.

Erin needs his help busting a scam ring that preys upon senior citizens. She'll probably want Henry to pose as a less aware older person than he really is so they can catch the would-be scammers red-handed.

This doesn't sound particularly dangerous, but that doesn't mean Henry's family will like it. Jamie tends to be protective of Henry, and Frank sometimes oversteps to protect his father.

It's always annoying when they do that. Henry may be in his 80s, but his mind is still sharp, and he doesn't need to be treated like he's fragile or incapable.

If anyone interferes with him working on this case, Henry will let them have it.

He doesn't appreciate it when his son or grandchildren treat him like he's one step away from the nursing home, and he's not shy about saying so.

Finally, Eddie helps search for a stolen puppy while her boss acts suspiciously.

There has to be more to this story than meets the eye. A stolen puppy doesn't sound like a compelling case, especially not for a senior cop like Eddie.

And if she's going to bring Sergeant McNichols down, it should be over something more important!

There are sure to be some surprises in store here. This may be all a set-up so that Eddie and Jamie end up adopting a dog or something similar.

Conversely, being given this type of ridiculous case could push Eddie to take the next step in her career. She's been adamant that she wants to stay on the streets, but if she's forced to take cases beneath her, she might decide to become a detective after all.

The stolen dog could be something other than a simple dog-napping, too. The animal might be a rare breed or worth a lot of money, or its disappearance could be tied to a major gang or other crime ring.

What do you think, Blue Bloods fanatics? Will Eddie's story be worth it? What are your ideas about the other storylines? Hit the big, blue SHOW COMMENTS button and let us know!

Don't forget you can watch Blue Bloods online whenever you want.

Blue Bloods airs on CBS on Fridays at 10 PM EST / PST. The midseason premiere airs on January 6, 2023.

Jack Ori is a senior staff writer for TV Fanatic. His debut young adult novel, Reinventing Hannah, is available on Amazon. Follow him on X.