He asked Harry on the tenth.
They were in the library after dinner — the specific late-evening configuration of two people in a room full of books who had stopped reading and were talking instead, which was a configuration the library at the Wulfhall had been producing since Hermione arrived and which he had found he valued in the specific way of someone who had spent a long time working alone and had discovered that thinking aloud with someone you trusted was a different and more productive kind of working.
'Gringotts,' he said. 'I need to go in and get the Horcrux from Bellatrix Lestrange's vault.'
Harry looked at him. 'You're going alone.'
'Yes,' Ron said. 'If I took anyone with me I'd spend most of my preparation managing their safety rather than the task. Alone I can move at my pace and make decisions without consulting.'
'The Goblin staff,' Harry said. 'The security. The vault doors.'
'The primary challenge is the Goblin I'll need to Imperius,' Ron said. 'I need the Goblin to maintain a convincing performance for the duration of the cart journey and the vault access, which is approximately forty minutes total. Standard Imperius breaks under sufficient resistance. The standard resistance a Goblin would offer is insufficient to break a properly cast Imperius.' He paused. 'My concern is the return journey.'
'Why the return specifically?'
'Because the Goblin will have been under for forty minutes by then,' Ron said. 'The longer the Imperius is maintained the more difficult it becomes to hold cleanly — the resistance accumulates. I need the Goblin to function exactly normally for the full duration.'
Harry was quiet for a moment. He had the quality of someone thinking through a problem rather than simply listening to it. 'In the graveyard,' he said. 'Voldemort put me under the Imperius. I threw it off. Crouch Junior — the fake Moody — put me under it in the first DADA lesson. I threw that off too.'
'I know,' Ron said. 'The interesting thing is that the Horcrux made it harder for you, not easier. A fragment of Voldemort's own soul sitting behind your Occlumency — it would have been pulling against any resistance to his influence, not reinforcing it. What you were fighting against in the graveyard was his Imperius and his Horcrux both at once.'
Harry was quiet for a moment.
'What you actually had,' Ron continued, 'was willpower. Specifically, the kind that doesn't negotiate. Two weeks of Occlumency training, yes, but mostly: you simply decided not to comply, and the decision held.' He looked at Harry. 'A Goblin has no Occlumency and no particular access to that kind of categorical refusal. It's not the same architecture.'
'Occlumency,' Harry said. 'That's still part of your calculation.'
'It's part of mine,' Ron said. 'I'm not asking you to hold it. I'm asking you to be the evidence that willpower alone can resist Voldemort's version. If that's the floor, a Goblin — with neither your willpower nor your external resistance factors working against them — is not going to break a clean Imperius in forty minutes.'
Harry absorbed this. 'You're using me as the evidence that the approach works.'
'I'm using you as the comparative data point,' Ron said. 'Voldemort's Imperius is stronger than mine. You resisted his. Therefore a Goblin with less inherent resistance than you and no external factors enhancing it will not resist mine for forty minutes.'
Harry looked at the bookshelf. 'That's a lot of confidence in a comparative data point.'
'It's a sound inference,' Ron said. 'I've also been practicing the hold since January.'
'Of course you have,' Harry said. He was quiet for a moment. Then: 'You're going to Obliviate them after.'
'Yes. The Imperius, the route to Bellatrix's vault, the access — all of it. Clean, targeted, nothing that damages the Goblin's function.'
'And if something goes wrong.'
'I have the Elder Wand,' Ron said. 'The wand signature masking is the most effective available. I'll be entering as myself — no glamour, no disguise, just Ron Weasley going to his own vault. The Imperius happens in the cart.'
'And if the Imperius breaks.'
'Then I improvise,' Ron said.
Harry looked at him steadily. 'So you have a plan, and you've thought about what happens when the plan fails, but you're not expecting it to fail.'
'Yes,' Ron said. 'That's an accurate summary.'
'Don't get caught,' Harry said.
'That's the plan,' Ron said.