"Hey! I think this worm just bit me!" Frodo complained, pulling his hand back from the pot of soil he had been about to plant some snapdragons and petunias in.
"But worms can't really bite," Sam replied. "They don't need teeth to eat dead leaves and are completely harmless as well as useful."
"But this one bit me! Look, it's even bleeding a bit!"
Sam looked at Frodo's hand and sure enough, a droplet of blood bloomed bright red at the tip of Frodo's index finger.
"Are you sure you didn't just snag your finger on a sharp stone or a shard of glass?" Sam asked, still doubtful. "This is just an earthworm, after all, not a dragon."
"Of course I'm sure!" Frodo said glaring down at the tiny creature squirming in the soil.
"Well, whatever it was, Mr. Frodo, let's wash the wound out to make sure the dirt is gone. After all you've been through, we don't want you catching wound fever over something so small."
They went inside, where Sam carefully washed and bandaged Frodo's finger as the full moon rose higher in the sky and the sun sank over the horizon.
The wound healed quickly and they soon forgot about what had happened.
...
One month later, Frodo hobbled into the kitchen where Sam was chopping carrots for lunch while Rosie tended little Elanor.
"I'm afraid I am unwell, Sam. I'm retiring for the day."
"But Mr. Frodo, the anniversary of the day you were bitten by Shelob has already passed and October is still far off," Sam said, remembering the days Frodo usually took ill.
"I know. Perhaps it is just an ordinary illness," Frodo said.
"Shall we get Healer Ruddles?" Sam asked, not reassured by Frodo's explanation.
"I'm sure it is nothing serious, Sam. Don't worry, I'll be up and about again tomorrow," Frodo replied.
"You will let us know if you need anything?" Sam asked.
"Of course I will," Frodo said. "Right now, all I need is some rest and I will be right as rain before you know it." He gave Sam a slightly pained smile before leaving the kitchen.
"Don't worry, Sam," Rosie said, bouncing Elanor up and down. "I'm sure he is right and will be up and about again soon enough."
Sam gave her a doubtful shrug, but went back to chopping carrots.
Sam decided that since Frodo had already missed lunch, it wouldn't hurt to see if he perhaps wanted some carrot soup for dinner. His Gaffer swore that carrot soup was capable of curing all ills and would give you a hawk's eyesight as well, though Sam was not quite sure why any hobbit would need a hawk's eyesight.
He knocked at the door to Frodo's bedroom carefully as not to disturb Frodo if he was sleeping.
"Mr. Frodo? I made some carrot soup. It would do you well to eat a bit…"
He carefully pushed open the door when there was no reply, just to make sure that everything was well. The curtains on the windows were drawn and the sheets on the bed were rumpled, but there was clearly nobody in the bed anymore.
"Mr. Frodo?"
That was when Sam noticed a movement on the floor where the light of the full moon fell through a crack in the curtains. He took a step forward and squinted at the little creature.
"Rrraaarghh!" said the worm, squirming towards Sam as quickly as it could.
Sam stared at it. Then he did what he often did when things confused him: he chose to sleep over it and deal with it in the light of morning. Still holding the bowl of soup, he left the room and closed the door behind him.
"There's a worm where Mr. Frodo should be," he told Rosie.
"Well, I don't want any worms in the smial. Take it outside or at least make sure it doesn't come into the kitchen."
Sam laid an old blanket in front of the crack under the door.
...
Frodo emerged from his room the following afternoon. He came into the kitchen, drank a large mug of water in one and immediately refilled it.
"I'm really thirsty; I don't know why. And I must have fallen out of bed tonight. I woke up on the floor."
"Not that you are accountable to me, Mr. Frodo, but where did you go last night? Is the worm still there?" Sam asked.
"Which worm? I didn't see any worm," Frodo replied, finishing his second mug.
Sam explained what he had seen the previous night, but Frodo couldn't remember anything except falling asleep in his bed and waking up on the ground feeling thirstier than he had ever before.
...
Sam tried to ask around, but nobody had noticed anything about worms acting strangely or heard about anyone getting bitten by a worm. And he could hardly state his suspicion that Frodo had been replaced by a growling worm for a night.
After several trips to the Green Dragon, the Dancing Swan and even the Fox and Hare over in Michel Delving resulted in nothing but a couple of severe hangovers and Rosie's displeasure, Sam turned to the books in Bag End's reading parlour. Finally, in a book titled 'Beasts of Rhûn and Beyond' which he assumed had been given to Bilbo by one of the dwarves that had always been visiting Bag End back in the day, Sam found a description of the were-worms of the Last Desert.
The book was written in a strange style and Sam was not entirely sure he understood all of it correctly. The description did not entirely fit the creature that had bitten Frodo either. For one, the worm in their garden had most certainly not been half as long as a grown man, not even that of a suckling babe, nor had it been bright red. Sam had not been able to see pronounced fangs on it either and it had not spit out destructive juices. Still, Sam resolved to keep a close eye on Frodo.
...
As it happened, Sam and Frodo were working in the garden the afternoon before the next full moon was to rise. Sam had made sure he was wearing leather gloves this time, just to be safe. He surreptitiously glanced at Frodo, noticing how he wriggled his toes in the loose soil, growing more and more restless.
"Are you feeling quite well, Mr. Frodo?" Sam finally asked. "You look a bit peaky. Do you want to go inside?"
"I do feel slightly unwell," Frodo replied, looking at the soil regretfully.
"We could take some soil inside in a box," Sam said, following a sudden impulse, "just in case, you know, you wanted to continue potting plants inside."
"That sounds like a strangely appealing idea," Frodo said.
Sam quickly got a box, filled it with soil and carried it as well as some plants that needed potting inside after Frodo, who had gone ahead. He set the box by Frodo's bed.
Frodo hovered by the box, running his fingers through the soil, though he didn't actually do any planting.
Sam stayed nearby, determined to get to the bottom of this mystery and at the same time hoping Frodo wouldn't suddenly turn into giant read worm spewing nasty substances at him.
"Sam? Could you perhaps get me a glass of water? I… oh."
Sam quickly turned away from the window where the full moon was just starting to peak over the trees. Frodo was gone. His clothes lay in an untidy heap on the box with soil.
"Mr. Frodo?" Sam asked, cautiously lifting the clothes off the soil.
"Rrraaaarrrrghh!" said the worm on the soil, lunging at Sam as best as a tiny worm can lunge.
Sam quickly pulled back his hand before the worm could do any harm and slammed the lid on the box.
"However will I explain this to Rosie?"