It is dinnertime at the castle. The main course of ox is being served when the conversation turns to tardy collecting of "delinquent" taxes in the north. Bertram says the latest excuse is plague, and goes into details about plague that ruin appetites (note this). Prince John then reads a proclamation that they are to send the royal seal (a live seal) to King Richard.
In the kitchen, the chefs realise they have mistakenly served contaminated ox meat to the table and it will make people sick. They quickly disappear without warning anyone.
Elsewhere, Robin and his men have the royal seal (the proper one), but are given misinformation about a short cut and end up in the banquet hall. The Sheriff serves them some of the ox meat before challenging them to the usual sword fight. But the fight is cut short when Bertram falls sick from the contaminated meat. He mistakes it for plague, having talked about it so much. Robin puts a 24-hour quarantine on the banquet hall, so he and his enemies are stuck together for that time. He is still determined to get the royal seal to King Richard while the Sheriff waits to see who will be left standing. During that time Robin and Marian have fantasies about their love. The Sheriff admits to Marian that he loves her too – only to find Robin standing there.
As the quarantine wears on, everyone falls sick until only Robin, Marian and the Sheriff are left. The Sheriff and Robin have another sword fight, but Marian forces them to stop by threatening them with a meringue pie. They settle down to eat, Marian and the Sheriff commenting that they have not eaten (Bertram made them lose their appetites earlier). Something clicks in Robin's head, and he realises that it was the meat and not the plague. But by the time he does, the Sheriff has eaten some of it and fallen sick himself.
As it was a simple case of 24-hour ox poisoning, everyone soon recovers. The Sheriff is left tied to a chair while Robin gets the seal (not the live one) to King Richard.