"A man is the sum of his memories you know, a Timelord even more so." - The 5th Doctor

The Doctor wandered the corridors of the TARDIS, hands thrust deep into the pockets of his striped trousers. After his most recent adventure he had decided he needed a little time alone. He had left Tegan and Turlough in the console room, arguing no doubt. He assumed Kamelion was in his room recharging.

Memories raced through the Doctor's mind. Times long past, long forgotten. Areas of memory he had long since closed off came bubbling to the surface of his mind. Good memories, happy memories. It was the context that made him sad.

He wasn't at all surprised to find himself outside a particular door. This door used to be a lot closer to the console room, but he had moved it a long time ago, not wanting to pass it every day. He was pleased it hadn't been jettisoned in the escape from Event One, early in his current incarnation.

Despite the fact he knew the door was sealed, he laid his hand on the handle. Another memory came to the fore, of the day he had sealed it. Much like today, he had escaped his companions and wandered the TARDIS alone, until he decided on his course of action...

***

The Doctor stood before the door, a thermal lance in his hand. He pushed the welding goggles up onto his forehead.

There, it was done. Finished. He could continue his travels now, knowing he would never open this door again.

A frown crossed his weathered face. The humans would call this closure. He called it sadness, loss, other feelings he had thought long buried deep in his mind.

He never thought this day would come. He had ignored the signs, until Barbara had taken him to one side and quietly pointed them out. It was then that he knew he would have to be the one who took responsibility, who made the first move.

He sighed. Now he had made the last move as well. Closure. The door was closed forever now, a part of him locked away inside.

The Doctor removed the welding goggles and ran his free hand through his damp white hair. Time to move on.

He turned, leaving the door behind and not looking back.

***

Now he was back, four incarnations later, his hand resting lightly on the handle. A sudden thought came to him and he was walking quickly down the corridor. He broke into a run, fawn frock coat flapping behind him.

***

A short time later, the Doctor was back. This time he was armed with a molecular debonder, which he aimed at the door seal. Slowly, painfully slowly, the seal began to dissolve.

Part of his mind told him this wasn't a good idea. But he still kept the device trained on the seal he had made so long ago.

After what seemed like an age, the last part of the seal boiled away and the door was free. Laying the debonder aside, the Doctor placed his hand on the handle once more.

There was still time to turn back, the practical part of his mind said. Turn around and walk away. Don't look back. But once more, this part lost the battle.

During a regeneration, some memories are always lost. The trauma of change makes this inevitable. But some memories remain fresh, even after four regenerations.

The room was just as he remembered it. All the little personal objects collected during so many travels to exotic places. So many memories.

"Hello, Grandfather," said a voice from the shadows.

"Hello, Susan," he replied, despite the fact he knew this was an illusion created by his own mind.

She looked the same as when they had met again briefly on Gallifrey. He hadn't had enough time to talk to her then.

"Any regrets?" she asked now.

He smiled sadly. "Too many to count," he said honestly. "But if you mean about leaving you on Earth with David, then no. It was the right thing to do."

She smiled broadly at him. "It was. Thank you. I would never have left you, you knew that. You had to make the choice for me."

"It wasn't easy," he told her.

She nodded. "I know. But David and I are very happy." A thought occurred to her. "Maybe you could visit us sometime?"

"Maybe," he said, knowing it probably wouldn't happen. The pain of parting was always too great. Maybe when he was ready to stop travelling and settle down. But he wasn't ready to retire just yet.

"I must be going," Susan said. "But I'm not really here at all, am I?"

"I know. It was nice to see you."

"You too. Goodbye, Grandfather."

"Goodbye, Susan," he said softly.

Heaving a sigh, the Doctor took one last look around, then stepped back through the door and closed it firmly behind him. He thought briefly about sealing it again, but decided against it. He wanted to come back here again sometime.

Smiling slightly to himself, he set off for the console room to see what trouble Tegan and Turlough were getting into.