Blue Bloods Season 13 Episode 12 involves doing the right thing when people fall through the cracks.

When a woman confesses in front of Frank that she killed her husband, Frank soon learns that she had an order of protection and called the cops often, but no one ever did anything to the man. Garrett and Sid don't think it's Frank's place to respond to this tragedy, but Frank feels the system failed this woman and that he needs to get to the bottom of it.

Frank's investigation leads to the revelation that the man was a CI and that the captain and his detectives ignored the woman's plight so that they could continue to use him to bust a drug dealing ring. Frank is disgusted and wishes he could perp walk the cops involved.

Meanwhile, Jamie arrests a thief who explains that he steals from constructions sites because the foreman stiffs immigrants and threatens to have them deported if they complain. He convinces Jamie to let him wear a wire to prove it, but the mission goes south.

And finally, Danny reluctantly helps his ne'er-do-well childhood friend with his missing fiancee while Erin goes on stakeout one last time before running for DA.

To find out what happens, watch Blue Bloods Season 13 Episode 12 online.