The alternative then, was to tell the truth - or as near to the truth as the situation allowed. The absolute truth was that he was serving his long-term strategy- looking to the greater plan. Whilst a spy belonging to his Master in any other position within the Rebellion would be an acceptable risk, Leemarit was the Communications Chief aboard the Rebel flagship and Luke's continued involvement with those onboard in handing over information, however unsympathetically, would result in an extended spell of 'correction' if his Master found out. Which there was a good chance of if the Comm Chief - the being who monitored all ingoing and outgoing comms - happened to be Palpatine's spy. It would be literally years before Palpatine would trust Luke again- before he would even let his precious Jedi out of his sight.
No; having finally found out the name of Palpatine's spy, he'd had to remove Leemarit as soon as possible, his access to all comms - those Luke sent to the Rebels and those Argot sent to him - was simply too dangerous to be allowed to continue.
His chosen course of action in having Leemarit assassinated then revealing the assassin - carefully timed to be too late to prevent it of course - had gained credibility and trust for his invented 'Imperial traitor' whilst ensuring the ongoing safety of Argot, Luke's own spy on the Rebel flagship. All this had been running in the background, hidden away beneath Luke's action against the Bothans, and it had worked perfectly - until now.
He had of course intended to be found out eventually anyway - or rather to come clean - but only when he had captured Mon Mothma and so proved his commitment to the Emperor. To do so now, with nothing to show for his questionable actions in removing Palpatine's long-standing spy, was a dangerous gamble.
Handing Mothma over was to be proof of his commitment and distraction from Luke's need to remove Leemarit. Explaining the finer details of how he'd achieved the capture of the elusive leader of the Rebellion - after he had done so - was to have been evidence of Luke's competence, both in terms of general experience and his familiarity and expertise in matters to do with the Rebellion.
And all of this to hide a greater cause; the definitive intent which had crystallised during his recovery and was now being pursued with relentless drive, engineered through subtle plays and hidden agenda's. But before he could set his greater plan in motion, Luke needed two things; control of the campaign against the Rebellion, and to create a certain mindset; guarantee a specific weakness in the Rebellion that he alone could exploit. One that would be invisible from the outside and from within.
Wheels within wheels within wheels - a precarious game for the highest stakes, just as his Master had taught him, in actions if not in words. But all this later, when the situation allowed; not now. Now it only clouded the issue. He'd only needed a week- two at the outside.
Can't be helped now. Move forward.
Palpatine was watching him expectantly...
Word it carefully- "I needed their trust to get to Mothma. Leemarit bought me that."
"You gave them my Rodian." Palpatine grated, eyes narrowed in threat, "He has been a reliable source of information for many years."
Luke didn't flinch beneath that gaze- perhaps he should have, just a little? Too late now- go with the plan; it was too early and he knew it, but concocting something under pressure would force mistakes and his Master was too wily an opponent to ever try such a gambit with. "I've replaced him. There's already another agent in place- I wouldn't leave us blind."
"And he is?"
"Trustworthy, Master. You taught me well." Oh, he shouldn't have said it like that. Luke saw his Master's eyes narrow, but he couldn't give up that information, not yet.
The Emperor didn't fail to notice the double meaning behind Skywalker's words, nor the fact that he didn't yield beneath his Masters obvious disapproval; didn't pass over this new agents name - well-taught indeed.
"There was no need to replace him." Palpatine grated, not caring about the agent, only that his Jedi had done this without his permission.
"For you, Master - for me, there was every need."
Palpatine only lifted his eyebrows in impatient expectation.
"He crossed me." Luke stated flatly, mind still racing, searching for something Palpatine would understand- believe. "Whether he knew who I was or not was immaterial. Three years ago he sold me out to the Alliance. You taught me never to leave a score unpaid, Master- what did you expect, once you gave me his name?"
The brief memory of his Wolf's interest when Palpatine had fist quoted Leemarit's name came abruptly to mind, though at the time Palpatine had assumed it interest in the information which had so completely condemned Mothma. Palpatine seethed at his own misreading of the situation, his anger turning instantly on the boy. Even if his reason for removing Leemarit was genuine, it was still done without his Master's consent.
"Besides," his Jedi added, neatly throwing out a second reason, equally valid, "It was a gamble to leave him in place- what if he'd been discovered? He knew far too much about Luke Skywalker - knew that he wasn't an Imperial... not at the time Leemarit implicated him. If they'd found out that the Rodian was your spy..." he left the rest unsaid.
"So you sold him to them. And now they'll check his past and question everything he's ever done - including uncovering you."
Too soon- too soon to be revealing this. It would only cloud the issue, Luke knew; jeopardize his chances to go after Mothma. But there was nothing to be done now except roll with the punches and watch for his chance to take the conversation back where he needed it. Trying to avoid or redirect it now would only make Palpatine more suspicious. "No Master. He died with his reputation intact- I sent a mercenary in to assassinate him. One who knew only that The Heir wanted revenge on the Rebel who had broken his cover. It was him I sold to the Alliance- after he'd done his job of course. I believe he was killed, but if not they can interrogate him all they want, he'll only corroborate their beliefs. I'd already put another agent quietly into position, completely unconnected. Someone I trust, well-placed."
"You have been planning this for some time." Palpatine said; this was no gut reaction- placing people within the Rebellion was difficult. Admittedly, as the boy had just illustrated by being able to do this, he knew their methods better than most, having fought alongside them for three years. But still, this was a long-term plan- even more than it first seemed, he suspected. Here was the reason behind his momentary burst of misgiving when Palpatine had first entered the room- as well it might be!
"As part of a greater plan, yes." The boy said, wary and rightfully so, since Palpatine had banned him from any involvement in hunting down the Rebels. "I wanted Mothma- you told me yourself that it was she who signed the order for my assassination... you knew I'd act on it."
"With my permission! I gave permission to go after those who had aided in the attempt within your jurisdiction."
Luke met the Emperor's eye; "Then give me the jurisdiction; give me control of the anti-insurrection task force."
Palpatine hesitated, momentarily thrown by the unprecedented request; by the raw desire in the boy's voice. Had his plan in spurring the Rebels to reject Skywalker been this successful? Because the desire, the need in the boy's appeal now sung out like a pure note in the Force.
It mollified him... somewhat. Calmed his tone as he settled back into his ornate throne. "Vader is charged with command of the anti-insurgency task-force."