Up in arms
I'm the Captain. I'm on a ship with Warwick and other prisoners. I can't stand Warwick's holier than thou attitude and I don't mind telling him he's not that special to his face. And you know what I think?
The princely Warwick, and the Nevils all,
Whose dreadful swords were never drawn in vain,
As hating thee, are rising up in arms:
And now the house of York, thrust from the crown
By shameful murder of a guiltless king
And lofty proud encroaching tyranny,
Burns with revenging fire; whose hopeful colours
Advance our half-faced sun, striving to shine,
Under the which is writ 'Invitis nubibus.'
The commons here in Kent are up in arms:
And, to conclude, reproach and beggary
Is crept into the palace of our king.
And all by thee. Away! convey him hence. (4.1.91-103)
Who Said It and Where
Warwick has been sent away because he murdered Gloucester. We meet up with the guy, in disguise, on a ship at sea that's under attack. A captain fills us in on the deets: basically, things aren't looking so hot right now. He decides to divide the prisoners up between himself and other masters on the ship. Some will be pardoned, others ransomed, and a select few, executed.
Suffolk is given to a man named Whitmore who will kill him. (Since it was prophesized that he would die by water, we're not thinking his odds look too good.) Naturally Suffolk starts chitchatting with Whitmore. As you do with your would-be executioner. After some back and forth about whether he's afraid of death, Suffolk reveals who he is.
Not only that, but Suffolk says he's too important and high-class to die by such low-lifes as themselves. At least he hasn't lost his bold edge. The Captain isn't buying it. He says Suffolk should be ashamed of himself for kissing the queen, smiling at Gloucester's death, losing lands in France, and calculating against a guiltless king. He shouldn't be all up in arms. Bam. He orders for Suffolk to be beheaded. Uh oh.
Again, Suffolk insists that he is too good for that. But his pleas are in vain. Whitmore is instructed to kill Suffolk, and that's that. As a last ditch attempt to save his life, Suffolk asks to send a message to the queen. He tells us that he won't beg for his life. Sometimes nobles die at the hands of commoners and he's not one to get all scared about it. He's escorted off stage by soldiers.
Moments later, Whitmore returns with Suffolk's head. Guess that solves that mystery.