He assumed Percy Weasley was related to Ron Weasley and his gang, which meant that he was the brother that was in close with the Umbridge woman. Using the imperius curse was always slightly disorientating for him because the jumble of emotions that came with most humans was almost overwhelming.
Percy was ambitious and hated his family for bringing him down, so even if the pureblood had known the first thing about imperius defence, it still would have been easy to persuade him to send a letter to Ron dissuading him from starting a defence against the dark arts class.
So he knew exactly when to be waiting at the window for Percy's owl and he managed to intercept it before it had even been noticed by the trio at the couches by the fire. They noticed him releasing the bird though, which ignited a flurry of concerned whispering. He almost caved, this would make their lessons much more difficult to schedule but he was certain Hermione would be up for the challenge and it would gain him an invaluable position in the circle Umbridge was building.
He knocked on the door, waiting until he heard the prim order to enter.
Umbridge's office was as pink as he remembered, although the slight feral cats on the plates he'd smashed on his last visit were missing, replaced by different ones. It was a shame, he'd hoped to find the slight discrepancy to keep his attention during what he expected would soon be numerous tedious meetings.
'What is it, Abernathy?' She asked, looking up from the essays she was grading.
'I found a letter, Ma'am.' He answered smartly, letting his accent burr through. The official put down her pink quill precisely, then looked at him with patronising interest.
'Does something in it concern you, Mr. Abernathy?' She asked, readjusting the high inquisitor sign on her desk.
'Yes Ma'am, I think you should see it.' He handed the letter to her and she took it with a little huff.
It took her a couple of moments to read it, her eyes darting like a frog following the path of a fly. He waited in silence, wondering if there was a way he could curse the plates into silence. The constant mewling was reaching the end of his nerved when Umbridge finally put the letter down.
'They're planning to train themselves?' She inquired, colour tingeing her cheeks. He remained silent as the woman dithered before finally snatching a sheet of pink parchment and scribbling a letter. She was pressing so hard with the quill that she carved grooves into the paper. It finally snapped as she scrawled her signature sending ink spraying across the room.
'Mr. Abernathy.' She called him back to focus and he snapped to attention. She tittered at the Durmstrang style salute. 'Oh you poor dear, Professor Dumbledore really hasn't helped you settle in at all. We don't make children do that kind of thing here.' She informed him and he struggled to keep his temper in check. The cats were beginning to give him a headache and Umbridge's patronising didn't help.
'I'm hoping to arrange a little group of students to help me keep things in check here at Hogwarts.' She continued, 'It would be a wonderful opportunity for you if you hope to go on to join the ministry.'
Gellert nodded, hoping he came across as eager; it wasn't an expression he'd tried to put on much.
'That's a good boy. Would you do me a favour and run this letter up to the owlery, it's for the minister.' He nodded and took the parchment, not needed to feign his eagerness to leave the room.
He dispatched the letter using a school owl, then returned to his magic room. It seemed to have settled as the planning room for the moment, so all of his notes had remained organised on their peg boards. He took a seat, then jumped when a pot of tea appeared opposite him a moment later.
'Winky?' He asked into the apparently empty room. The squeaky reply came from the other side of the table as a plate of dinner appeared.
'Winky thought Master Gellert would like some dinner. Winky also thought Master might be interested to know that Harry Potter and Hermione Granger are on their way here with Dobby.'
He nodded, thanking the elf and taking a sip of the tea. As usual it was perfect, even cooled to not burn his mouth. He drank it quickly but asked Winky to bring the dinner to him later. The young elf preened as he praised her quick thinking and then disappeared with a pop as Gellert cast a disillusionment on himself.
He left the room, tucking himself behind a brazier so the flickering of the flames would disguise the slight discrepancy caused by the charm. He only had to wait a while before he saw Harry and Hermione appear from around the corner, led by an elf dressed in an absurd collection of hats and socks. Ron would still be in detention with Umbridge.
'Here Harry Potter, Sir.' The elf pulled the duo to a halt right in front of where Gellert sat. 'Harry Potter must think of what he needs very hard.'
The elf dragged them back and forth in a pattern Gellert had walked many times, then a different door appeared in the wall. This one was much larger than the one to Gellert's planning room, double metal doors that towered above the student's heads. Hermione pushed open the door and the duo slipped inside, leaving the door ajar. Gellert slipped in behind them, listening to their explanations of awe. Hermione stood by a well stocked booksheld, reading the titles and barely containing her glee as she announced the most exciting ones. Harry on the other hand was more interested in a large pile of dummies and decorative pillows.
'This is perfect Hermione!' Harry exclaimed, moving on to join Hermione at the bookshelf.
'We should schedule a meeting, let's let everyone know at breakfast tomorrow.'
Gellert left then as the duo made their way towards the door. He doubted scheduling the meeting would be as simple as they anticipated. Umbridge was almost certain to have come up with a way to stop the defence classes. That would make it a little more difficult to find out when the meeting would be held but he was certain he was up to the challenge. Hermione would have an army of friends to protect her by the time the year was out.