When they reach Dagobah, they found Yoda to be very weak. Dooku realized, in horror, that his old mentor was sick and quite possibly dying.
"Become one with the Force I soon shall."
Dooku paled and reached for his Master when a coughing spell hit him. He cradled his teach in his lap.
Luke got a bowl of warm water and a soft rag. He dampened it and handed it to Dooku. The old man gently patted the tiny Jedi's forehead, fighting back tears. He had always thought that Yoda would out-live him.
The hours passed slowly for the two younger Jedi as they kept watch over the ancient Master.
Dooku had abandoned the rag and was now merely stroking Yoda's head as Yoda had always done for him when he was a boy and had been sick or scared.
Luke watched sadly. He had grown fond of Yoda, but he knew that this was tearing Dooku apart. He reach for him through their mental bond.
Sorrow, denial, and self-anger washed over him from his teacher.
"Forgive me, Master," Dooku said, choked by tears.
"Your fault this is not."
The man sniffled.
"I should have been here to take care of you."
"More important... matters you... had."
Cradling him in his arms, Dooku nuzzled his great head on his Master's chest. Yoda weakly stroked his hair.
"Always... with... you... will... I... be,... my... son."
Grand Master Yoda passed into the Force at last.
For the first time in year, for the first time since Padme died, Dooku wept.
Luke bowed his head sadly. He went outside to think. He spoke to Obi-Wan's spirit, learned that Leia was his sister, and meditated for a while.
He went back inside to find Dooku curled up in his bed like a frightened, lost child, clutching a tiny lightsaber hilt to his chest.
Luke pulled a blanket over his mentor, gently brushed a stray lock of hair from the man's face, and began to make some dinner.
Dooku awoke just as Luke finished dinner.
"What do we do now?"
The Master's face hardened with resolve and determination.
"We complete out mission; we destroy the Empire."