The Weasleys arrive at the Dursley's by Floo powder.
"What is it?" gasped Aunt Petnunia, who had backed into the wall and was staring, terrified, toward the fire. "What is it, Vernon?"
But they were left in doubt barely a second longer. Voices could be heard from inside the blocked fireplace.
"Ouch! Fred,no---go back, go back, there's been some kind of mistake---tell George not to---OUCH! George, no, there's no room, go back quickly and tell Ron---"
"Maybe Harry can hear us, Dad---maybe he'll be able to let us out---"
There was a loud hammering of fists on the boards behind the electric fire.
"Harry? Harry, can you hear us?"