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Here’s what you need to know:

Inside the New York terrorist plot.

• Sayfullo Saipov, 29, started planning a year ago for the attack that killed eight and injured 12 others, choosing to carry it out on Halloween because more people would be on the streets, federal prosecutors said.

Mr. Saipov, who came to the U.S. from Uzbekistan in 2010, led a rootless life that eventually turned to radical Islam. “He did not learn religion properly,” one imam said.

Although the charges Mr. Saipov faces describe him as a student of Islamic State propaganda, the militant group has not claimed responsibility for the rampage. Rukmini Callimachi, who covers ISIS for The Times, explains why.