On Blue Bloods Season 9 Episode 19, Luis Delgado again returned, this time to avenge his wife's death and maybe Linda's too.

Isabel Delgado calls Danny to tell him someone broke into the house and the cops are taking forever to come, but she is killed before she can complete the call. At the scene, Delgado shows up to comfort his kids, who were hiding in a cupboard, and is arrested. A DEA agent tells Danny that Delgado is their CI and that he may have info related to Linda's death.

Delgado wants to get Jose Rojas, the killer, but only if Danny will work with him. Danny reluctantly agrees to this mission, but can Delgado be trusted?

Meanwhile, Jamie arrests an obnoxious drunk at a bar fight who proudly proclaims that he stabbed a guy. The victim dies, but the perp walks because he was drunk when he made this confession and Jamie didn't get it in writing later. Jamie blames Erin for this snafu and the two cannot see eye-to-eye on this one despite Jamie's understanding of the legal issues Erin had to deal with.

And Frank has headaches of his own to deal with when Eddie's mother shows up in his office demanding special treatment because her daughter is marrying a cop, yet doesn't want to report several crimes against her in her building for fear that it will hurt Eddie.

To find out what happens watch Blue Bloods Season 9 Episode 19 online.