Plymouth 400 September 4, 2021 11:23 pm Plymouth 400 Celebrations Underway A year later due to the pandemic, Plymouth celebrates its founding 400 years earlier. US & World Videos 3:05 100 protesters detained at Northeastern University 2:39 Community mourns police sergeant killed on duty 2:50 Community mourns Billerica police sergeant killed on duty 4:32 Anti-war protester at Northeastern speaks amid arrests: ‘We are peaceful students' 10:42 Multiple people arrested as police clear campus encampments