Nancy woke with a jump to find Violet standing over her, shaking her shoulder. She sat up and rubbed her eyes.

“Someone’s banging at the shop door,” said Violet anxiously, pulling on Nancy’s arm. “I heard shouting so went downstairs. They said to open up. It’s the police.”

Leaping out of bed, Nancy ran to the window, gingerly parting the curtains to peep down to the street below. Two policemen in black helmets stood on the shop doorstep. Bang, bang, bang, bang. “Open up, Mr Greenstone,” one of them shouted.

Nancy let the curtains drop from her fingers in alarm.

“What in heaven’s name is happening?” Nancy heard her mother call.

Nancy flung open their bedroom door. Her mother was tying the cord of her dressing gown round her waist as she stood on the first-floor landing.

“Wait, Charlotte. I’ll go,” her grandfather called out, appearing a few seconds later in his nightshirt. They both continued down to the ground floor, not paying Nancy or Violet the slightest attention.

Nancy felt a quell of nausea as she followed them downstairs. Her mother was hovering in the ground-floor hallway.

“No…she’s not here,” she heard her grandfather say from within the shop.

“We have witnesses,” said a voice – one of the policemen.

“But I live alone, have done for years,” said her grandfather.

“Don’t try and pull the wool over our eyes, Mr Greenstone. If you don’t fetch your daughter right this minute, we will be forced to search the house.” The policeman’s voice was low and determined and meant business.

Nancy saw her mother shift position. She glanced up the stairs and Nancy shrank back into the shadows, but she had been seen. Nancy was about to go downstairs when her mother raised a hand, instructing her to stay where she was. She touched a finger to her lips signalling for Nancy to be quiet, then she was gone, walking into the shop.

“I am here,” Nancy heard her mother say. “There is no need to search the house.”

Nancy lowered herself slowly until she was sitting on the stairs. She pulled her knees close to her chest and hugged them.

“Miss Greenstone, you have returned,” one of the policemen said in surprise. Her mother didn’t reply.

“A return which almost had rather devastating consequences for Mayor Douglas last night,” said a different, more gravelly voice – the other policeman.

“The mayor?” her grandfather said. “What does he have to do with your visit?”

“As if you don’t know,” said the first policeman, in an unpleasant sneering tone. “Miss Greenstone, I am arresting you for attempted arson – for trying to burn down the mayor’s house. I need you to accompany me to the police station for questioning.”

Nancy felt the hair lift at the nape of her neck. “Arson?” she whispered. Their mother had tried to burn down the mayor’s house? She heard a creak and looked up to see Violet creeping downstairs. She came and sat next to Nancy, so close their arms bumped together. Nancy clasped her knees tightly, waiting for Mother to tell the policemen they had made the most dreadful mistake.

“Tell them, Charlotte. Tell them you did not do this,” urged their grandfather.

“We have a witness,” said the gravelly voiced policeman. “And evidence.” There was a pause. “You were seen pushing a burning handkerchief through the mayor’s letter box last night…a little after ten in the evening.”

“No!” exclaimed their grandfather. “That is not what happened!”

Violet dragged in a sharp breath and reached for Nancy’s hand.

This was ridiculous. Their mother was the wife of an upstanding solicitor and pillar of the local community. She attended church each week in Leeds. Said grace before mealtimes. She was not an arsonist. With all of her being, Nancy willed her mother to speak up and defend herself.

“Charlotte Greenstone…I am arresting you for the…”

“Yes, yes,” said her mother sharply, finding her voice at last. “I heard your accusation the first time. I haven’t used the name Greenstone for many years. I am Mrs Rivers now. You have a case of mistaken identity. Now please leave.”

One of the policemen barked out a snarling laugh that made Nancy shiver. She pressed her palm into her sister’s hand and gave Violet what she hoped was a reassuring look.

“Do you happen to own any handkerchiefs with red-ribbon edging?” the policeman said. “They are very distinctive…and we have it on good authority that you sew these handkerchiefs yourself.”

There was a long pause. One of the handkerchiefs that Nancy and her mother embroidered had been used to commit the crime. But how could that be?

“Yes, it sounds like one of mine but…” began their mother.

“And were you, or were you not, in the vicinity of the mayor’s house just after ten o’clock last night?” interrupted the policeman.

A heavy silence settled on the house.

“Careful now, Miss Greenstone. Remember, we have a witness,” said the deep-voiced policeman, as triumphantly as if he’d just caught a fish he had been trying to hook all day.

“Yes, I was there but…” said their mother tightly.

“There we have it then,” said the other policeman. “What a sorry situation. Mr Greenstone, you may fetch your daughter’s coat, then we are taking her to the police station.”

“May I please get dressed first?” requested Mother, her voice trembling a little.

“No time for that,” replied the policeman.

Nancy bit hard on her bottom lip. This couldn’t be happening.

“Mayor Douglas,” their mother said in a small voice. “Is he…was he…hurt?”

The air in the hallway seemed to constrict, squeezing Nancy’s lungs. Violet smothered a small gasp.

“No. It is lucky the witness to the crime banged on his door to alert him,” said one of the policemen. “If he had perished you would be facing a far worse charge.”

Pinches of dread needled at Nancy’s skin as she realized that their mother was being arrested for an unimaginable crime, and that she had not protested her innocence. The mysteries she was facing had suddenly taken the most terrible and dangerous turn.