Neville was sleeping in the Forth Year Gryffindor Boys Dormitory when he was woken up by someone touching him. He opened his eyes to see a house elf. He tried to scream, but no sound came out.
"I put a silencing charm on you, so you don't wake the other boys. It will be gone in a few minutes. I just came to warn you. The Trophy, for the last task, is a portkey, which will take you to a graveyard with death eaters."
With that, the house elf vanished.
Neville told Hermione what happened, first thing the next morning. They went to see Professor Dumbledore, before breakfast. They did not want to take the time to go and get Jane and Luna, so they'd just tell them about it later.
Weeks later, Neville returned to the library, after being summoned to Professor Dumbledore's office. He was glad to find that the girls were still there.
"Great news," Neville said. "The cup was a portkey but it's been replaced by a new one, that's not."
Jane sighed. "Good. I wish there was a way to thank the house-elf."
Neville had thanked Mrs. Snake for her help over Easter break, but he wasn't sure if he would ever see Dobby again. Later, he thought of an idea.
In the kitchen, Neville explained what had happened.
"That must have been Dobby," one of the house elves said. "I can apparate over there tonight, and send a message for you."
"Thank you, so much," Jane said.