Ron found Harry and Hermione using the Deluminator. It released a ball of energy that somehow (insert plothole here) guided him to his friends' location.
‘So I took it out,’ Ron went on, looking at the Deluminator, ‘and it didn’t seem different, or anything, but I was sure I’d heard you. So I clicked it. And the light went out in my room, but another light appeared right outside the window.’
Ron raised his empty hand and pointed in front of him, his eyes focused on something neither Harry nor Hermione could see.
‘It was a ball of light, kind of pulsing, and bluish, like that light you get around a Portkey, you know?’
‘Yeah,’ said Harry and Hermione together, automatically.
‘I knew this was it,’ said Ron. ‘I grabbed my stuff and packed it, then I put on my rucksack and went out into the garden.
‘The little ball of light was hovering there, waiting for me, and when I came out it bobbed along a bit and I followed it behind the shed and then it … well, it went inside me.’
‘Sorry?’ said Harry, sure he had not heard correctly.
‘It sort of floated towards me,’ said Ron, illustrating the movement with his free index finger, ‘right to my chest, and then – it just went straight through. It was here,’ he touched a point close to his heart, ‘I could feel it, it was hot. And once it was inside me I knew what I was supposed to do, I knew it would take me where I needed to go. So I Disapparated and came out on the side of a hill. There was snow everywhere …’
‘We were there,’ said Harry. ‘We spent two nights there, and the second night I kept thinking I could hear someone moving around in the dark and calling out!’
‘Yeah, well, that would’ve been me,’ said Ron. ‘Your protective spells work, anyway, because I couldn’t see you and I couldn’t hear you. I was sure you were around, though, so in the end I got in my sleeping bag and waited for one of you to appear. I thought you’d have to show yourselves when you packed up the tent.’
Once he found Harry, Ron swam down to collect the Sword of Gryffindor from the bottom of the lake and used it to cut the Horcrux off of Harry's neck.
Nothing but the shock of hearing that voice could have given Harry the strength to get up. Shivering violently, he staggered to his feet.
There before him stood Ron, fully dressed but drenched to the skin, his hair plastered to his face, the sword of Gryffindor in one hand and the Horcrux dangling from its broken chain in the other.
*‘Why the hell,’ panted Ron, holding up the Horcrux, which swung backwards and forwards on its shortened chain in some parody of hypnosis, ‘didn’t you take this thing off before you dived?’