A child being kidnapped outside of her school had Danny remembering a similar case from seven years ago on Blue Bloods Season 4 Episode 15.
If Danny's own memories of failing to find Allie weren't enough, he had to contend with Allie's dad showing up and still holding out hope that his daughter would be found.
I give the actor who played Joseph credit. Even as he thought and acted rationally he always had that haunted, half-crazed look in his eyes. It was the look of someone who'd been forced to walk through a living nightmare for seven years.