A man sprays a woman heading into the subway.

Her lips turn blue as she coughs, then collapses and dies.

Isobel completes Maggie's positive annual performance review.

Maggie tells Isobel she's considering IVF. Isobel pledges her support.

The dead woman at the subway is Angela Lane, who works at the Bureau of Land Management.

The medical examiner suspects she was killed by a fast-acting form of ricin.

There were no witnesses to her being attacked.

The victim's sister said Angela had a restraining order against her ex-husband, Eric, a domestic abuser.

Eric got laid off from his job in biotech.

He resists arrest by Scola and Tiffany.

Eric has an alibi as he was meeting with his divorce attorney.

Angela did have a stalker but it wasn't Eric.

Tracking the suspect's car, Maggie and OA come upon another woman who's been gassed.

Maggie gives chase but he escapes after they scuffle.

They watch the second infected woman die.

The second victim is Sharon Williams, a lobbyist for Thornhill, whose biggest client is Green Solutions, a fracking company.

Jubal draws the conclusion that the killer is an eco-terrorist.

Isobel brings in Maggie's friend Jessica from Counterterrorism.

New legislation would reinstate fracking in New York.

A shipment of the beans used in the kind of ricin used was received by a lab at Hudson University.

The beans are missing from a locked refrigerator.

The lab director's asisstant, Landon, who had access to the beans, went home sick.

Landon runs from Maggie and OA but they catch him.

Jessica went into Landon's apartment and they find her passed out.

Jess is awake and taking oxygen as she's hauled away by an ambulance.

Landon admits that he's the chemist who created the ricin. But he won't give up the names of others involved.

His father and lawyer arrive to end the questioning.

Jessica calls Maggie to let her know it wasn't ricin that caused her to collapse. But she asks Maggie to pick up her daughter Ella.

The next step is to figure out who radicalized Landon. Scola and Tiffany track down Sarah, who they thought was his girlfriend. She steers them to a violent student named Anthony Jackson but she's still arrested.

Sen. Daniel Drew, who sponsored the fracking bill, is likely the next target.

Maggie approaches Anthony and he sprays ricin toward her and runs.

Maggie shoots when he whips out a can after being caught.

Jess calls and tells Maggie she had a mild aneurysm. She names Maggie as Ella's temporary guardian as she has to undergo surgery.

NYPD reports another ricin attack across town. The victim, Mary Byrne, is alive. She has no connection to fracking. The ricin used on her was diluted.

Mary's brother is a policy advisor to the governor. He's been called by a woman threatening his family.

Sarah is still in custody. Professor Celeste Johnson, head of the Hudson lab, was the one who called Bobby Byrne.

Johnson is heading to Green Solutions.

She's putting the ricin through the sprinkler system. The building isn't cleared out yet.

Maggie finds the main sprinkler unit and tries to shut it down but Johnson attacks her.

Johnson broke off the shutdown lever. OA finds vice grips to turn it off.

When Maggie arrives at the hospital, Jessica is still in surgery.

Jess dies on the table and Maggie is left to break the news to Ella.