The image of Ron's arms -- little more than meat -- was still flashing through Harry's mind as Hermione left.
He cast tracking, detection and revealing spells, and then cast a few more that were considered on the boarderline of Dark. The only thing he found were traces of blood on Ron's side of the bed.
"We're going to, Ron. Just as soon as we figure out how," he said to the empty room. With a slow turn, he cast a sealing spell that would close the Floo and Apparation points, and alert him if anyone tried to enter the flat. He then wove several tracking spells into the ward that would attach themselves to Ron if he returned, however briefly.
Oh, god, Ron. Harry dropped to his knees and allowed the despair he'd been feeling to overwhelm him. Later, there would be Leila and wet cheek kisses and Hermione and logic and hugs. But for now, there was just the hollow ache for his best friend, needing his help and being unable to reach him.