The three went down to the living room, and the Doctor sat on the sofa. The Professor went over to the mantelpiece to look at some pictures, while Clara decided to make them some tea.

"So, who was she?" Clara asked. "The lady with the funny name and the space hair?"

"An old friend of mine," the Doctor said.

"What, like an ex?" Clara asked.

"Kinda. It's hard to explain," the Professor said. "Timelines are."

"River asked Vastra for the exact words. What were they?" the Doctor asked.

"'The Doctor has a secret he will take to the grave.'," Clara said, bringing the cups over to them. "It is discovered.'"

The Doctor looked down, and he closed his eyes. He was silent for a moment. He was in deep thought as he let the words run through his mind. The words chilled him to the bone.

"Dad?" The Professor asked, going over.

"Sorry," the Doctor apologised. Tears began to form in his eyes. "And it was Trenzalore? It was definitely Trenzalore?" he asked, his voice breaking.

"Yeah," Clara said.

"Oh, dear," the Doctor whispered, then spoke in a normal tone, "Sorry." He got up in a rush and exited the house. He needed to clear his head, and he wanted to do so privately.

"Well, that was weird," Clara said.

"Must have brought back his past," the Professor said, holding Clara's hand and starting to walk with her to follow his father.

They made their way to the TARDIS and entered the ship. They took the stairs that led them to the area below the console room. Once they were under the console, the two found the Doctor sitting on top of the cupboards.

"Well?" Clara asked.

"Trenzalore. I have heard the name, of course," the Doctor began. "Dorium mentioned it, a few others … We all suspected what it was, never wanted to find out myself." The Doctor stood up and sonicked the cables above. "River would know, though. River always knew." He picked a wire and held it in his hand. "Right. Come here, Clara. Give me your hand." The Professor and Clara both went up to where the Doctor stood. The Professor wrapped his arms around Clara's waist while she outstretched her hand. "Now, the coordinates you saw will still be in your memory," the Doctor continued. "I am linking you into the TARDIS telepathic circuit. Won't hurt a bit."

Knowing what was going to happen, the Professor began to kiss Clara's neck in hopes of distracting her long enough. The Doctor pricked Clara's hand with a wire from the TARDIS, but it broke Clara's concentration from the neck kisses. "Ow..." she said.

"I lied," the Doctor said as the circuitry made a whining tone.

"So, what is Trenzalore?" Clara asked. "Is that your big secret?"

"No."

"Okay. What, then?"

"When you are a time traveller, there is one place you must never go. One place in all time and space you must never, ever find yourself."

"Where?"

"Your grave," the Professor said. "The Great Intelligence was talking about Dad's Grave. Not his secret."

The Doctor nodded. "Yes. And it is that that has been discovered. Trenzalore is where I'm buried," he said, then walked up the stairs.

Clara and the Professor turned around, following. "How can you have a grave?" Clara asked.

"Because we all do somewhere out in the future, waiting for us. The trouble with time travel, you can end up visiting."

"But you're not going to. You just said it's one place you must never go."

"I have to save Vastra and Strax. Jenny, too, if it's still possible. They cared for me in dark times. Never questioned me, never judged me. They were just … kind. I owe them. I have a duty towards them. No point in telling you this is too dangerous?"

Both the Professor and Clara looked at each other and smiled. "None at all," Clara said. "How can we save them?"

"Apparently, by breaking into my tomb," the Doctor said, flipping a lever and starting the engines. The control room filled the air with the ancient wheezing and groaning. Both the Professor and the Doctor tried to fly the TARDIS, but the ship was too strong-willed. It had figured out where they were planning on heading and wanted to stop it from happening.

"What's that?" Clara asked.

"Well, the TARDIS has figured out what we're planning on doing," the Professor said. "And she's against it."

The Doctor grabbed two switches and tried to pull them down. "I'm about to cross my timeline in the biggest way possible. And the TARDIS doesn't like it. So she's fighting it."

"Hang on, Clara!" the Professor said, as Clara held on to the console as tight as possible.

As the two Time Lords forced the ship to Trenzalore, sparks flew out of the console before shutting down and stopping suddenly. It halted so abruptly that it created enough force to push the three away from the console.

"Now what?" Clara asked.

"She's shut down everything because she doesn't want to land," the Professor said.

"So, we're not there?"

The Doctor had gone over to the console, trying to flick some controls. "We must be close," he said, going over to the doors and opening them. Once opened, he saw the planet below. A ravaged world with rivers of lava. "Okay. So that's where I end up." The Professor and Clara went over. "I always thought maybe I'd retire, take up watercolours, bee-keeping, or something. Apparently not."

"So, how do we get down there?" Clara asked. "Jump?"

"Don't be silly! We fall," the Doctor said, shutting the doors before heading for the console. "She's turned off practically everything except the anti-gravity. Guess what I'm turning off?" He took out his sonic screwdriver and aimed it at the console. Then, giving it a quick whir, he turned off the anti-gravity. The TARDIS lost orbit and fell towards the planet when the anti-gravity was turned off. As they fell towards the world of Trenzalore, the Professor held on tightly to the TARDIS railing, with Clara holding on to him.

Once the TARDIS landed on the planet, the Doctor walked out first and noticed a crack in the windows. He rubbed it and said, "Oops."

The Professor and Clara followed him out on the stormy planet. There were gravestones strewn everywhere, and ivy had started to grow on some.

"You okay?" Clara asked. "Visiting your own grave, anyone would be scared."

"It's more than that," the Doctor said. "I'm a time traveller. I've probably time-travelled more than anyone else."

"Meaning?"

"His grave is one of the dangerous places in the universe," the Professor said.

"Shall we?" The Doctor asked.

The Professor and Clara nodded as they began to walk with the Doctor. "The gravestones are a bit basic," Clara noted.

"It's a battlefield graveyard. My final battle," the Doctor explained.

"Why are some of them bigger?"

"They're soldiers. Bigger the gravestone, higher the rank."

They climbed over a small hill and saw a decaying TARDIS. It was significantly more massive than the TARDIS that they had come from.

"It's a hell of a monument," Clara said. "It's the TARDIS," the Professor said.

"I can see that."

"No. When a TARDIS is dying, sometimes the dimension dams start breaking down. They used to call it a size leak," the Doctor said. "All the bigger on the inside starts leaking to the outside, and it grows. So it is the TARDIS. My TARDIS from the future." The Doctor started to walk forward. "What else would they bury me in?"

The Professor put an arm around Clara when she heard a voice. "Clara!" River said. "Don't speak. Don't say my name. They can't see or hear me. Only you can."

"Well, come on then!" The Doctor called back to them.

"We're mentally linked. It's the conference call. I kept the line open."

The Professor turned around to see what Clara was looking at when he saw a small gravestone. "Dad...You may want to see this..." he called back.

The Doctor went over to them. "What are you looking at? We need to get..." But he couldn't finish his sentence when he saw the gravestone too. "River?" He asked softly, staring at her tombstone. He went over to it and fingered over the engraved writing.

"That can't be right," Clara said, looking at the gravestone.

"Of course not," the Professor said. "How could she die here when she died on another planet a long time ago?"

"She's dead?"

"Yeah," River said to Clara. "I probably should have mentioned that. Never the right time."

"But I met her."

"Long story," the Doctor said. "But her grave can't be here."

While they were musing River's tomb, Clara could hear some whispering. She turned around. "Doctor! Professor!" She said, and they turned around, seeing the Whispermen approaching.

"This man must fall, as all men must," they uttered. "The fate of all is always dust."

The Doctor tried to work his sonic screwdriver at them while the Professor conjured up a fireball and aimed it at them. But the fireball just passed through the Whispermen.

"If it isn't my gravestone, then what it is?" River asked.

"What do you think that gravestone really is?" Clara repeated to the two Time Lords.

"The gravestone?" The Doctor asked back.

"Maybe it's a false grave," River said. "Maybe it's a false grave," Clara repeated. "Maybe," the Professor said.

"Maybe it's a secret entrance to the tomb," River said.

"Maybe it's a secret entrance to the tomb!" Clara repeated.

The Doctor spun around. "Yes. Of course. Makes sense," he said, whirring his sonic screwdriver at the tomb. "They'd never bury my wife out here."

Clara spun around as the Professor put his arms around her. "Your what?" She asked.

As the three fell, the Whispermen crouched down over the grave. "The man who lies will lie no more. Where this man lies, it's Trenzalore."