“That’s amazing. Gertrude is innocent.”

“And so am I.” Laura glanced across the room. “What’s he eating? Wilbur, what have you got in your mouth? No, Wilbur, no!” She dashed across and forced open the dog’s jaws. A small piece of mincemeat fell into her palm. “Rosemary, look. There are crumbs on the carpet. I think he’s had a mince pie.”

Rosemary was already at her side fingering the pastry crumbs. “It can’t have come from inside the house. The police spent over an hour searching the place.”

“The garden, then,” Laura said. “He must have found it in the garden.”

They went to the front door. “Let him show us,” Rosemary said. “Find it, Wilbur. Good dog.”

Wilbur knew what was wanted. He went straight to a lavender bush and lifted it with his nose. A brownish conical thing was exposed.

“A death cap,” Rosemary said.

“Do you mind?” Laura said. “That’s pastry. That’s one of my lids.” She picked it up and turned it over. “How on earth did this get here?”

The question hung in the air unanswered. Wilbur’s cooperation could only go so far.

“Should we get him to a vet?” Laura said.

“Let’s give him water first.”

Rosemary filled his bowl and brought it to him. He lapped it obediently.

“He doesn’t seem to be suffering,” Laura said. “The onset was rapid with Douglas Boon.”

“Taxin is one of the quickest of all the plant poisons,” Rosemary said. “I doubt if we’d get him to a vet in time.”

“He looks all right.”

Wilbur licked her hand and wagged his tail.

“I think he wants some more.”

An hour later, he was still all right.

Rosemary and Laura allowed themselves the luxury of fresh tea. They didn’t get to drink it because Wilbur unexpectedly barked several times and ran to the door. Someone was outside holding a flashlight.

Laura looked out. The evening had drawn in and she had difficulty seeing who it was.

The voice was familiar. “You’d better call the police,” Gertrude Appleton said. “I’ve gone and killed another man.”

“This can’t be true,” Laura said. “You’re in the clear. Your pies were analysed today and there’s nothing toxic in them.”

With a stare like the condemned woman in a silent movie, Gertrude said, “Follow me,” and started towards the gate.

Laura looked at Rosemary. They’d been in dangerous situations before. Rosemary shrugged. At least Gertrude wasn’t wielding that cleaver. They went after her.

She paused at her garden gate and turned the flashlight beam on Rosemary and Laura to check that they were behind her. Then she led them to her greenhouse and unlocked the door.

The place would have been creepy even in daylight, with a huge overhanging vine that still had some of its leaves, brown and contorted. Other skeletal plants in pots had been brought in for the winter. Gertrude edged around a raised flower bed in the centre and directed the flashlight at a dark shape on the floor.

A man’s body.

“I killed him,” Gertrude said with a stricken sigh. “I never looked here when I smoked out the pests on Christmas Eve. I just put down the stuff and set light to it.”

“He is dead, I suppose?” Laura said.

Rosemary leaned over for a closer look. “Well dead, I would say.”

Gertrude was still reliving the experience. “I made sure it was smouldering and got out, locking the door behind me. Opened it an hour ago and found him. I can only suppose he was drunk and crept in here to sleep it off.” She paused. “Will I go to prison?”

“Let me have the flashlight,” Laura said. She edged past Gertrude for a closer inspection. “I can’t say I know him intimately, but isn’t this one of the carol singers, the tall one, Balthazar?”

“Ben Black? It is!” Gertrude said in despair. “God forgive me. What have I done?”

“Unless I’ve got my facts muddled, you haven’t done anything at all,” Laura said. “You fumigated on Christmas Eve after visiting me, am I right?”

Gertrude nodded.

“That was in the afternoon? You locked the door and didn’t open up until today? You left the key in the lock?”

Another nod from Gertrude.

“Think about it,” Laura said. “Ben was alive and singing carols that same evening. He couldn’t have been trapped in here. See, there’s dried blood on the back of his scalp. It looks as if someone hit him over the head and dumped the body in here. Yes, we will call the police, but I don’t think you’re in any trouble.”

Over cocoa that night, with the dog asleep in front of a real log fire, Rosemary summed up the case. “What we have are two impossible crimes. One man poisoned by a harmless mince pie and another bludgeoned to death in a locked greenhouse.”

“The second crime isn’t impossible,” Laura said. “The key was in the door. Obviously the killer could get in and out. They put the body in there and locked it again thinking it might not be found for some time.”

“They?”

“Could be a man or a woman. That’s all I mean.”

“Then are we agreed that there’s only one killer?” Rosemary said.

“Let’s hope so.”

“So why was Ben Black bumped off?”

“Because he knew something about the first crime?”

“Very likely. And why did the first crime take place?”

“The death of Douglas Boon? It could have been a mistake,” Laura said. “Maybe he ate a poisoned pie intended for Ben Black.”

“I don’t think so,” Rosemary said. “Remember, Douglas was a gannet. He was guaranteed to take any pie that was offered except one of Gertrude’s.”

“Hers were on the heavy side,” Laura recalled.

“So if we assume Douglas ’s death was planned and carried out in cold blood, what did Ben find out that meant he had to be murdered as well?”

“It’s got to be something to do with the mince pie Wilbur found under the lavender bush,” Laura said.

“Another harmless pie?”

They were silent for some time, staring into the flames. “Do you think that young vicar is all he seems?” Rosemary said.

Laura frowned. “I rather like him.”

“A bad sign, usually,” Rosemary said. “Let’s go and see him tomorrow.”

“Won’t the police say we’re interfering?”

“They’re going to be ages getting to the truth, if they ever do. For them it’s all about analysing DNA evidence, and we know how long that takes. A good old-fashioned face-to-face gets a quicker result.”

Overnight it snowed and they both slept late.

“It’s the total silence, I think,” Laura said. “I always get a marvellous sleep when there’s a snowfall.”

“Whatever it is,” Rosemary said, “I’ve had a few ideas about these deaths and I’d like to try them out on you.”

After breakfast they put on wellies and took Wilbur for his longest walk yet. He was more frisky than ever, bounding through the snow regardless of that mince pie the day before. People might spurn Gertrude’s cooking, but this hound had thrived on it. Along the way, they kept a lookout for yew trees, and counted five in and around the village, and three yew hedges. Over a pre-lunch drink in a quiet corner of the pub, Rosemary unfolded her theory to Laura and it made perfect sense. They knew from experience that theories are all very well, but the proof can be more elusive. They decided to go looking for it late in the afternoon.

“Are we clear about what each of us does?” Rosemary said.

“All too clear,” Laura said. “You get the inside job while I wait out here with Wilbur and freeze.”

“He’ll be fine. He loves the snow and he’s got his coat on. Just stroll around as if you’re exercising him.”

They had parked outside the village church.

Rosemary went in and found the vicar slotting hymn numbers into the frame above the pulpit.