It is the middle of a moonless night when the people of Birmingham are awakened by a scream coming from the streets. Someone has been murdered, they soon hear, but no body was found. Everyone gathers in the central square, looking for answers.
They all rightfully know that the Bishop would have been the only person awake and outside at the time of the events. Disfigured in his early childhood by a disease that has affected thousands, he (like most of the few survivors) has never shown his face to anyone since then, became a monk to thank God for sparing his life, and usually comes out only at night time.
When people come knocking at his door, he refuses to open as they would have expected. Instead, he speaks out the terrible truth that no one had been willing to see: "Someone from Worcester came during the night. Count the children."
They soon confirm that one of the teenage boys is missing. A group of investigators is formed, and starts heading towards Worcester, accompanied by knights and diplomats.
In Worcester, they find that most of the city is out in the streets as well, with every child under the supervision of an adult. The Earl of Worcester advances towards them and speaks:
"One of my children has gone missing, and two knights including the one who was guarding him were found dead. Several of my people claim that a bishop from Birmingham is responsible for this crime."
– "My Lord, we are terribly sorry to hear what happened here. Yet Birmingham has suffered the loss of a child as well, a teenage boy who was an expert in French, who cannot be found anywhere."
– "Serves you right!" someone shouts from the crowd. "You struck first!"
And as every face is turning to the corner where the voice came from, a child turns up and hands out a piece of paper to the Earl of Worcester. "Not everyone is who they claim they are", he says, and vanishes again into the crowd.
On the piece of paper, a chess board has been drawn:
What really happened during this dreadful night?
Hint #1:
Part of the answer requires completing the French sentence with one word, in French.
Hint #2:
Who struck first and how do you know that? Where are the boys now?