Disclaimer: Everything belongs to Professor Tolkien, of course. I'm just borrowing, as usual. All the dialogue, except maybe one line near the end, comes directly from The Two Towers ("The Palantír") and The Return of the King ("The Passing of the Grey Company").
This was written in response to Can We Talk?'s challenge: Best Friends.
Almost before Merry knew what was happening, Pippin had been whisked away from his side by Aragorn and set atop Shadowfax before Gandalf. "Farewell!" Gandalf called to them. "Follow fast! Away, Shadowfax!" Like an arrow from Legolas' bow, the mighty horse shot away, disappearing into the night, and taking Merry's little cousin with him.
It seemed impossible. Pippin couldn't be gone, just like that! He'd always been there beside Merry. It had been that way from the time Pippin had been old enough to follow Merry around every time their families visited. They had explored the Shire together, and terrorized Bag End for years. Bilbo had taught them both about Elves and Dwarves. When he had begun forming the Conspiracy, Merry had gone to Pippin first, knowing he could count on the young Took to aid him.
Now he was alone. Merry took a deep breath and looked up at Aragorn, forcing himself to speak lightly. "A beautiful, restful night!" he remarked. "Some folk have wonderful luck. He did not want to sleep, and he wanted to ride with Gandalf – and there he goes! Instead of being turned into a stone himself to stand here for ever as a warning." No, instead he was flying from danger into danger. Merry remembered enough from maps he'd seen to know how close Minas Tirith was to Mordor.
"If you had been the first to lift the Orthanc-stone, and not he, how would it be now?" replied Aragorn. He still watched the horizon, as though he could still see Shadowfax, though the horse had long since vanished into the darkness. "You might have done worse. Who can say?" He looked down, and squeezed Merry's shoulder comfortingly, and Merry knew the Ranger saw right through his cheerful façade. "But now it is your luck to come with me, I fear. At once. Go and get ready, and bring anything that Pippin left behind." He turned away to speak to Legolas, and added over his shoulder, "Make haste!"
Merry nodded and hurried to do as he was told. There was not much to gather, only a few things he had picked up in Isengard, since his pack was long since lost. It looked so terribly small next to Aragorn, Legolas, and Gimli's things, Merry thought. He could well relate; he felt quite small as he listened to his companions speak of the road ahead.
And now it seemed that his path was soon to be sundered from even Aragorn, Legolas, and Gimli! "Your road lies with him, I think, Merry," Aragorn said, speaking of the King of Rohan. "But do not look for mirth at the ending. It will be long, I fear, before Théoden sits at ease again in Meduseld. Many hopes will wither in this bitter Spring."
Merry looked up at Aragorn, whose expression was so terribly grim, and wondered what Pippin would have said to that. Likely something about food and a bed; the Took's cheerfulness was impossible to quell, it seemed, and everything was darker and more dismal without him around. Merry had not realized before how he depended on Pippin for his own good spirits. He had nothing to say to try to lighten the weight of Aragorn's words.
At last they were ready to depart. "Come, Merry, you will ride with me." Aragorn lifted Merry easily onto Hasufel's saddle, and sprang into the saddle behind him. Gimli rode behind Legolas on Arod, and they joined Théoden King and his men. They set off at a swift pace, and Merry took a deep breath. Many hopes would wither that Spring, Aragorn had said, but not all. Merry would not let his own hope wither. He would come to Minas Tirith somehow and find Pippin. And together they would do whatever it took to aid Frodo and Sam in their quest. He'd even face a Nazgûl if it would help them.