When a gas leaks into a bus, three MTA workers collapse. Jubal's ex-wife Sam finds a walnut-size lump on his son Tyler. She's rushing him to see his doctor. Two of the MTA workers die. The bioweapon has botox. It had been set to go off at 5 p.m., when the bus would have been packed, but a mechanic set it off by mistake. OA and Scola find the bus driver who installed the weapon shot and floating in the river. He was recruited by a Yemeni terror group. Tyler's doctor orders an ultrasound. The team attempts to track the toxin, who came from Hudson University. A suspect, Amal Janubi, runs when OA and Scola try to question her, but is caught. She was working for Bin Zada, who has enough toxin for another bioweapon. She blames America for the Saudi bombing of Yemen. Another attack is planned for that night. Jubal snaps at his team. He has to admit to Isobel what's going on with Tyler. Isobel sends him out into the field with Maggie. A fruit vendor identifies Hassan Nasif, whose mother's maiden name was Zada. Hassan escapes from Maggie and Jubal, wounding Maggie with a brick. The man Hassan is working with is his cousin, Ahmad. They track Admad's van and get into a shootout. Armed with the aerosol, the terrorists run into Grand Central Station. The team attempts to evacuate the building. The terrorists split up. Tiffany kills the fleeing Ahmad. Maggie disagrees with Jubal about tactics and she's afraid he's drinking again.Hassan won't talk. Maggie theorizes that the aerosol is in the HVAC system. She checks a vent and finds the device. Ian talks her through deactivating it. Afterward, Maggie urges Jubal to get help. Tyler has a cyst that just needs draining.