Blue Bloods Season 12 Episode 18 revolves around difficult choices.

When a Captain Phillips saves a woman from being pushed onto the subway tracks, he asks to meet Frank. Garrett is uncomfortable from the get-go, while Abigail thinks Denzel Washington should play Phillips in a movie. Phillips wants to join the force, but he's almost 42 -- too old to join up. He wants Frank to make an exception.

Meanwhile, Jamie sees Sergeant Nichols punch another cop in the nose and debates whether he should report her. Eddie encourages him to do so because she likes this woman and knows she is going through a hard time, but Jamie also knows the rule book says that he should file a report.

Finally, Erin runs into an old classmate who snidely informs her that her office doesn't care about justice and in fact convicted the wrong man. Erin and Anthony begin to look into the case, but they quickly hit a dead end and must rely on her annoying ex-colleague to solve it. The evidence quickly leads to a potential killer that the original department overlooked.

To find out what happens, watch Blue Bloods Season 12 Episode 18 online.