Bill McKibben (@billmckibben) has led the charge against the Keystone XL pipeline, and now he's taken his climate fight to Harvard. (Starts at 0:44)

Are officers behaving in a deadly fashion the tipping point in the debate over police body cameras? Boston Herald columnist Jennifer Braceras (@MAHockeyMom), former State Senator Warren Tolman (@warrentolman) and Collete Phillips Communications president Collette Phillips (@ColettePhillips) weigh in. (Starts at 8:25)

150 years ago, President Abraham Lincoln was assassinated by actor John Wilkes Booth at Ford’s Theater in Washington. Historical fiction writer William Martin (@Martinbooks) talks about “what if.” (Starts at 19:39)