Hostilities resumed in early 1355 when negotiations for the release of David II of Scotland - captive in England since the Battle of Neville's Cross in 1346 - finally collapsed. The English raided first, burning the Border lands of Patrick V, Earl of March. March wanted retribution, and he had the means to take it. Douglas joined him with his contingent. Sixty French knights, sent north under the Auld Alliance to harass the English on a second front while their own king prepared for war in France, supplemented the Scottish force. The combined army marched to the Merse, the rolling Borders country between the Tweed and the Lammermuirs. Their target was Norham Castle on the south bank of the Tweed, the great Bishopric of Durham stronghold that guarded the lower river. Their plan was an ambush.

Ramsay's raid drew Grey out exactly as intended. Grey had sent scouts to look for the main Scottish force; the scouts found nothing because Douglas and March had hidden their men in woods south of Duns, well clear of the obvious search routes. Lord Dacre rode with Grey. The English pursuit was professional but blinkered. Ramsay deliberately abandoned the stolen livestock and rode north, drawing the chase deeper into the Merse. When Grey finally saw the banners of March and Douglas rising from the wood line, the trap had already closed. Douglas and March moved between the English and the border, cutting off retreat. The Englishmen charged the Scots in front of them. The Scots had the numbers. The battle did not last long.

The Scots won and took valuable prisoners: Lord Dacre, Sir Thomas Grey himself, and his son who had been knighted that very day. Their own casualties were light - John Haliburton of Dirleton was the only nobleman of note killed. What happened next is the part of the battle that the chroniclers preserved with a kind of grim particularity. Most of the common English soldiers, captured alive, were bought by one of the French knights. He had personal reasons. The knight's father had been killed by the English in some earlier action, and he wanted revenge in kind. He had the captives massacred. The local people gave the place a name they did not forget. They called it Slaughter Hill.

Norham Castle held; the garrison there refused to surrender even after Grey's defeat. The Berwick garrison heard of the fight and marched south expecting to find Norham besieged. Instead they ran into Douglas, March, Thomas Stewart, 2nd Earl of Angus, and the French knights, who counter-attacked and seized Berwick town - though not its castle. Unable to take the citadel, March ordered the town burned and withdrew. The Scots' triumph was brief. Edward III of England marched north with a major army, drove into Scotland, and laid waste to Lothian in an episode the Scots remembered as the Burnt Candlemas. A successful Border ambush, in the wars of the fourteenth century, was rarely the end of anything. It was usually only the beginning of the next campaign season.