The series showcases what happened in 1993 in Waco, Texas when cult leader David Koresh faced off against the federal government in a siege of 51 days. In the first episode, gunfire erupts when federal agents arrive at the Branch Davidian compound with a search warrant. Hostage negotiators later attempt to get the children out of the compound.
David Koresh was a member and later a leader of the Branch Davidians, a religious sect and offshoot of the Davidian Seventh-day Adventists, a movement based at the Mount Carmel Center outside Waco, Texas. His apocalyptic Biblical teachings attracted various followers. He became subject to allegations about polygamy and child sexual abuse by former Branch Davidian associates, although investigation by authorities found no conclusive evidence. Further allegations related to the Branch Davidians' stockpiling of weapons led the FBI to launch a raid on the group's Mount Carmel compound in February 1993.

Curiosity over the man calling himself a messiah makes Waco the center of a media circus. FBI negotiation and rescue teams clash over the use of force. The negotiating team established contact with Koresh inside the compound.
Communication over the next 51 days included telephone exchanges with various FBI negotiators. Koresh himself had been seriously injured by a gunshot. As the standoff continued, he and his closest male associates negotiated delays, so that he could possibly write religious documents, which he said he needed to complete before his surrender. Koresh's conversations with the negotiators were dense and they also included biblical imagery. The FBI negotiators treated the situation as a hostage crisis.

The world waits as Koresh makes new promise of surrender but the FBI's controversial tactics turn the compound into an apocalyptic scene. U.S. Attorney General Janet Reno approved recommendations of FBI officials to proceed with a final advance in which the Branch Davidians would be removed from the Mount Carmel Center by force.
In an attempt to flush Koresh out of the stronghold, the FBI resorted to pumping CS gas into the compound with the aid of an M728 Combat Engineer Vehicle, which was equipped with a battering ram. In the course of the advance, the Mount Carmel Center caught fire under circumstances that remain disputed. Barricaded inside the building, 79 Branch Davidians perished in the ensuing blaze; 21 of these victims were children under the age of 16. Koresh, then 33, died of a gunshot wound to the head during the course of the fire. It is unknown whether he committed suicide or if he was killed.

The series follows the tragedy that occurred when terrorists attacked at the annual Boston Marathon on April 15, 2013. They carried out the attack by placing two homemade pressure cooker bombs which detonated near the finish line of the race 14 seconds and 210 yards (190 m) apart. That resulted in three fatalities and hundreds injured, including 17 who lost limbs. With the help of archive footage, interviews with investigators, witnesses, survivors, and occasional reenactments, it offers details about the FBI investigation into what was quickly deemed a domestic terrorist attack.
In the first episode, hours after the blasts, investigators pore over evidence. One photo and a few seconds of footage lead to a breakthrough - and an agonizing choice.

The images of brothers Tamerlan and Dzhokhar Tsarnaev are released to the public setting off a violent chain of events. Meanwhile, clues from their past tell a complicated story - how was the radicalization of the ethnically Chechen brothers and the existence of potential collaborators. The post-9/11 biases played a role in the investigation.

Following their identification, the Tsarnaev brothers killed an MIT policeman, then kidnapped a man in his car. They had a shootout with the police in nearby Watertown, during which two officers were severely injured (one of whom, Dennis Simmonds, died a year later). Tamerlan was shot several times, and his brother Dzhokhar ran him over while escaping in the stolen car. Tamerlan died soon after.
An unprecedented manhunt for Dzhokhar ensued, with thousands of law enforcement officers searching a 20-block area of Watertown. Residents of Watertown and surrounding communities were asked to stay indoors, and the transportation system and most businesses and public places closed. After a Watertown resident discovered him hiding in a boat in his backyard, Dzhokhar Tsarnaev is cornered into an intense standoff. As officials navigate remaining questions and suspicions, the city emerges Boston Strong.