"Poor hens," thought Tommy. Whatever it was that got them had been inside the hen house as it ate them. Grandma Claire had thought the hens had been carried off over the fence, as skunks have been known to do. These two had been killed before Grandma had covered the night lock-up pen with wire fencing over the top, evidently.

The killer had taken time to dig a hole as if it lived inside the hen house. But how had it got in? Surely Grandma would have smelled a skunk living in there. Maybe a raccoon?

Tommy followed the wire chicken tunnel to the duck pen. Grandma had seen mammal tracks in the snow one morning going through this tunnel. The tracks had been almost as small as a cat's, too large an animal to go through any cracks between boards of the hen house even before Grandma patched them.

Tommy crossed over to the chicken pasture connected to the scratching pen by a second wire chicken tunnel. A pile of black feathers marked where Omaha was killed during the period when the hens were roosting in one of the Osage orange hedge trees in the hen pasture. That was after something spooked them so badly in the hen house that they refused to go back. And whatever it was, it had injured Blanche's foot so that she dragged it for a week. No hens disappeared that time. Grandma thought an owl must have killed Omaha in the tree.

Tommy went into the duck pen and sat on the low duck house to think. Basila the calico cat jumped up beside him and rubbed against his arm, purring. He stroked her tri-colored coat as he thought out loud.

"Grandma Claire and Grandpa Jim need all the predators because when there are too many rabbits, they eat the bark on young trees and kill them. But now instead of hunting rabbits, they've killed all of Grandma's fowl, every last one. It's as if they all decided at once to stop eating rabbits and eat fowl instead."

He thought again about the hole in the earth in the hen house. "It was too small for a skunk or a raccoon. Maybe a weasel. But a weasel would kill the whole flock at once, not over a period of three months."

Basila liked being talked to. She stepped into Tommy's lap and put her claws in and out of his pant legs as she walked around on him, purring. "Ouch! Quit it!" Tommy pulled her claws out of his jeans and set her back on the roof beside him. "You're a good hunter, Baz, I know. You even catch grown rabbits sometimes." He took her face in his hands and looked sternly into her green eyes with their vertical slits. "But are you SURE you're not the one who killed those hens, Baz?"

Tommy knew that when she was only six months old, Basila had killed three of Grandma's hens, including Amelia, the favorite. Over a period of a week, each hen was pecking at something through a fence when Basila pounced on her head from the other side. Grandma didn't even suspect the culprit was Basila until Grandpa almost caught her in the act. Then he spanked her and scolded her and she never did it again-that anyone knew of.

Basila looked serenely back at Tommy. He released her face and petted her head. "I guess you didn't know then that killing chickens isn't allowed. But now you know better." Tommy sang the Basila song to the tune of "Sweet Georgia Brown" to let her know her hunting skills are appreciated:

She's a super-duper mouser, sweet Basila!
Sees a rat and she's a pouncer, sweet Basila!
She's our rodent depopulator, sweet Basila!
Hunt 'em down, eat 'em up, clean up the paw;
She's a world-class rodent hunter, sweet Basila!

"But," he sighed, "you're not much help now. As a hunter, I thought you could advise me about this case, but all you think of is purring and petting. This is serious business, you know. I've got to solve this mystery so Grandma can figure out how to build the new hen house so none of these chicken killers can get in. Grandma tore down the old hen house because she couldn't make it safe, no matter how hard she tried."

Tommy got up, went out the duck pen gate and crossed the creek on the tire dam. Basila went with him, as she often did, to keep him company. "We won't have any eggs," he told her sadly, "until Grandma can build a new hen house and buy some more hens from the Amish family over by the river."

Such pretty brown eggs they had been with their deep yellow yolks. Grandpa and Grandma liked to scramble them up with fresh vegetables and herbs from the garden.

Greta and Yolanda bleated their greetings as he opened the gate to the goat corral and went in. Basila easily walked through the six-inch mesh fence, but then had to make a dash for a hedge tree because Greta liked to butt cats.

"Shame on you, Greta; picking on Basila just because Yolanda picks on you." But Tommy knew it was no use to scold. In goat society, the bigger always knocks around the smaller who knocks around the smaller yet. He was glad he wasn't a goat.

Tommy went into the barn to investigate. Some hens must have roosted in the haymow above, for he could see their droppings still lying on the wooden floor. After the first two were killed, the last hen, Twilight, slept on the haystack in the paddock.

He left the barn and walked to the six-foot circle of fencing that held the haystack. Yes, there was Twilight's nest, a hole in the side that the goats had probably eaten out through the six-inch mesh.

Basila jumped down from the tree to the haystack and looked at Tommy's head but decided against jumping on it. Near where Basila crouched, Tommy saw a pile of Twilight's pretty black, red, and gold feathers. Something probably pounced on her in her sleep as she roosted there.

Basila jumped to the ground when Tommy headed for the gate and went through it with him. He fastened the gate behind them and stepped around the corner into the milking barn, a room partitioned off the rest of the goat barn. Basila followed. She listened attentively for a moment, staring at one of the feed barrels. Tommy noticed her interest and climbed up on the milking stand to look in it.

"Oh!" he cried in surprise. Dark eyes in a pointed gray face stared up at him. "Possum!" The barrel smelled of scat. Tommy's mind was racing. Opossums climb trees, eat rabbits and other rodents or fowl if they can get at them. It could have killed the hens in the barn and haystack and tree, but it was too large to go through the two-by-four-inch mesh of the lock-up pen or the narrow cracks in the hen house or the hole in the earth inside it.

The opossum bared its fangs at him, afraid because it was trapped. It looked very thin, sickly, and pitiful even with its fangs bared. Grandma had been feeding the goats out of a different barrel for weeks and hadn't looked into this one lately. Tommy wondered how long the poor thing had been without water. He saw it was only half grown, maybe Basila's age when she killed hens. Would it go back to the woods and hunt rodents if they turned it loose? Or kill Grandma's new hens when she got them?

Tommy left the opossum in the barrel and went up over the hill and around a bend in the creek to the site where Grandma had begun to build the new hen house. He was looking at the four corner posts she'd set into gravel when a movement off to the side caught his eye. It wasn't Basila. She'd gone to a brush pile searching for a rabbit's nest.

Tommy stood very still and watched. "A baby 'possum!" he whispered to himself. It didn't see him, but ambled up to the new hen pasture fence and easily crawled through the mesh.

"That's it!" That was how that opossum got through the fence and into the hen house! It went there last spring as a baby! It made a burrow inside the hen house and came out after the hens went to roost in the evenings. In the night lock-up pen, it could eat left-over chicken feed and drink from the chicken waterer.

Then in the fall when it was as big as Basila, it tried to catch Blanche as she roosted in the hen house. It must have grabbed her foot, but she jerked it out of its teeth, waking up all the hens in the commotion. They all ran away through the tunnel to their pasture. They refused to return to their hen house, so the opossum had eaten chicken feed for a few more weeks.

One night it had gone through the tunnel, climbed the tree and seized Omaha as she slept. The other hens moved after that to the duck pasture. By then it was winter. The opossum went through the other tunnel, leaving tracks in the snow, and killed more hens. It was big enough now to attack the big Muscovie ducks, killing even the old drake, Hamlet, who was nearly as big as a goose.

It had taken nearly a month to find out where the last three hens were hiding after they flew over the fence, crossed the dam and moved into the goat barn. They must have flown to the top of the low duck house first and then flown over the fence from there, Tommy reasoned.

Maybe the opossum knew where they were but was afraid of the goats. However, it was, hunger must have finally driven the opossum to enter the goat pen, probably at night when they were sleeping.

And when at last all the hens were dead, it must have jumped down into the barrel after the last few grains of milo. Tommy ran to tell Grandma what he'd figured out.

She was flabbergasted. "You mean all the time I was patching up the hen house and putting a wire cover over the night lockup pen, the 'possum was INSIDE?"

"I'm sure that's how it happened," Tommy said.

"We'd better go get that baby 'possum!"

"Grandma Claire, let's not kill it," Tommy said, running after her. "Let's just take it far away into the woods." They crossed the footbridge.

"Okay." Grandma knew, too, how much wild predators are needed to keep nature in balance. Without enough coyotes, foxes, opossums, raccoons, skunks, weasels, owls and hawks, there would be so many rodents they would kill all the young trees, eat up the gardens and eventually eat everything green. Any creature that multiplies without check will in time destroy its habitat.

Tommy ran to the tree he'd seen the baby climb. "There it is." He pointed to a branch halfway up. Grandma found a forked stick, then she and Tommy threw Osage oranges at the baby opossum until it fell out of the tree.

Grandma ran to it, pinned its neck down with the forked stick, picked it up from behind its neck and held it in a semi-choke at arm's length. It could neither bite nor scratch her as she and Tommy walked up the hill, across the prairie and deep into the woods of the game preserve. Then Grandma threw the baby opossum as far as she could throw. It landed in dry leaves and scurried away.

"Now what shall we do with the 'possum that killed all my hens and ducks," she asked Tommy.

"Could we take it to the woods, too?" Tommy asked. "It was just doing what came naturally."

They walked back to the milking barn and looked into the barrel. "We would be bitten if we reached in to get it," Grandma said.

"Let's try to roll the barrel out on its bottom rim." They got the barrel out of the milking barn and rolled it slowly up the hill. They dared not tip it much or the opossum would run out. At last they got it to the crest of the hill on the bank of the creek.

Tommy looked down. They were on an eroded cliff where the bank sheered away steeply a long way down to the creek. "I'm too tired to roll this barrel all the way to the game preserve," Grandma said.

"Me, too," Tommy admitted. "Let's tip it over the edge of the cliff here and drop the 'possum out."

"Okay," Grandma agreed. "Maybe the hard bump he'll get when he lands will teach him to leave farms alone and go back to the woods where he belongs." So that's what they did. The thin opossum bounced as it hit, but scampered off uninjured, heading east toward the preserve.

Grandma gave Tommy a big hug. "Thank you, Tommy, for solving the mystery of the fowl killer. I'll build my new hen house up on stilts with a big, hinged door so I can look in often to be sure no varmints are living in there."

"To think that it was only one half-grown 'possum and not a whole army of wood predators," Tommy said as they walked back to the house.

"That's amazing," said Grandma. "I'd never have guessed."

Back in the house, they felt hungry after so much walking. Grandma got out some raisins, pumpkin seeds, and dried apple slices. Tommy got the ceramic pitcher of morning's goat milk and glasses.

Bet that 'possum was glad to get a drink from the creek," Tommy said as he wiped off his mustache of rich milk.

"Hope he knows how to hunt rabbits," Grandma said between slices of apple. "Last winter hundreds of rabbits nearly killed many of our young apple trees."

"He's pretty smart, I think," said Tommy.

"He sure fooled me," said Grandma.

Through the windows they watched Basila crossing the crater with a baby rabbit dangling from her jaws. Tommy looked sad, feeling sorry for the dead baby rabbit.

"Think like an apple tree," said Grandma.

"Good hunter," said Tommy, meaning Basila.

"Good detective," said Grandma, meaning Tommy.

"Just doing what comes naturally," Tommy said with a grin, tapping his head.