In the library, the Doctor finds a mug.
Sitting harmlessly on the tabletop, pale and blue with the tiniest of chips on its rim, it startles him, and he crosses the room towards it slowly, as though it’s a polar bear he’s stumbled on.
There are two very good reasons there should not be a mug in the library. For starters, he doesn’t use that mug. He’s got mugs from Tryksofarian that hold temperature indefinitely. He’s got mugs from Maddagan VI that let you set the internal temperature within an eightieth of a degree Celsius. This mug — well, it’s just a mug, boring and ceramic, and he hasn’t used it himself in years.
And in any case, regardless of mug, it’s been months since he was in the library. It’s been months since he spent any decent amount of time on the TARDIS, what without eight-hour layovers as part of a daily routine, and the prospect of finding a mug he hasn’t used in a room he hasn’t been in is, frankly, unsettling.
He picks it up gingerly and peers inside. What were once no doubt the last dregs of coffee or tea have evaporated, leaving in their wake a faint brown rim at the bottom of the cup. He frowns at the stain. He considers Alice in Wonderland, the drinks she drank and the food she ate. He considers the types of things people usually put in mugs and the general improbability of a stowaway drinking his coffee and reading his books and leaving his mugs dirty on his coffee tables.
Then he runs his index finger along the bottom of the mug and pops the finger into his mouth.
Coffee, it tastes like. One sugar and entirely too much milk. He pulls the finger from his mouth and sighs.
Well, mystery solved. No mysterious stowaway, unless that mysterious stowaway happens to have the same precise taste as Donna Noble.
Readily associating the uncomfortable shift in his stomach with licking months-old coffee residue rather than any ridiculous sentimental reason, the Doctor leaves the library.
After he’d first lost her, the task of de-Rose-ifying the TARDIS had been painful and drawn out. In the years that she had traveled with him the girl had somehow managed to leave her mark in every nook and cranny in ways he’d previously have believed impossible. Shirts and shoes and scraps of paper and magazines and photos sprawled across the TARDIS, tossed haphazardly onto sofas and chairs, lying half-hidden under tables. When he'd finally worked up the nerve to sweep it all into one room, the TARDIS had felt bare.
With Donna, though, there’d been time to collect her things and return them to her. Traces of Donna on the TARDIS are few and far between, and the dirty mug is the first in quite a long time. Aside from the vast amount of space and the frankly incredible wardrobe, there is little to indicate that the TARDIS has ever held more than one passenger.
Nor will it, ever again.
He rinses the mug at the kitchen sink and thinks of the confused disappointment on Lady Christina’s face. It isn’t something he regrets, turning her down; it was the better of two choices and — for him at least — the road less traveled, so at bare minimum he had Robert Frost’s approval.
Still, the Doctor wonders whom precisely he’s washing this mug for, if he never intends to use it.
Donna would be furious, he knows. She’d be furious at him for a whole host of things, he’s sure, several of which would earn him a good smack, and right near the top of that list would be his blatant refusal to take the advice she’d given him years ago. He can practically hear the lecture.
You giant bloody prawn, she’d say, shaking her head as she did so. Are you completely daft? Haven’t we been over this? Do I need to write it backwards on your forehead so you see it when you’re fixing your hair? You need someone, you idiot. So go find Lara Croft and her hover bus and quit moping around!
He scrubs at the inside of the mug with a vigour he usually can’t manage over tasks like cleaning dishes. It’s impressive, really, how difficult removing the stain is proving to be, and the Doctor is hardly going to be bested by a mug. He reaches into the cupboard beneath the sink and sifts through his large assortment of alien cleaning products.
Rose would be furious too, he thinks.
You told me once, she’d say, and maybe she’d be blinking back angry tears the way she was when he last saw her, that it was the most important thing. Getting across the universe, you needed a hand to hold, you said, more than wormhole refractors and spaceships and whatever else. What, did you change your mind?
“Aha!” He pulls a strangely shaped bottle of viscous green liquid from the cupboard and straightens. The people of Kretchla are notoriously cleanly and their detergent is a force to be reckoned with. He pours a liberal amount into the mug and resumes his scrubbing, and really, he ought to visit Kretchla more often, though unknowingly leaving mugs of coffee to fester for several months was unlikely to win him any fast friends.
Sarah and Martha wouldn’t like it, either.
You’ve always traveled with others, Sarah would reason, and Martha — Martha, she wouldn’t say anything at all. She’d only look at him sadly, the full extent of her compassion and sympathy and pity hidden beneath a thin veneer of disapproval.
The Kretchlan detergent does absolutely nothing to the stain.
Admitting defeat to a mug is, he thinks, one of the more pathetic moments in his nine hundred years. He pops the cap back on the bottle with just a hint of a petulant scowl — he really will have to visit Kretchla, if only to inform them that their detergent is disappointingly sub-par — and stares at the mug.
He ought to throw it out. He’s certainly not lacking in mugs and one with a chip and a stain is hardly going to be missed by — well, him. It’s clutter, really, even if he isn’t pressed for room. He doesn’t need it.
Striding across the room, he moves to toss it in the bin.
You see, that pain, in there, comes Donna’s voice, and it’s memory, this time, rather than speculation. That doesn’t mean you were wrong to let her in. It proves you were right.
The Doctor pauses. He considers the bin and he considers the mug, chipped and stained. He considers the woman who’d used it last and the dozens of others who used it before her.
“You’re wrong,” he says — aloud, though the moment is long past, because the TARDIS is too quiet these days.
The answering silence is uncomfortable. Before he retreats back to the console room to find somewhere new to land, he opens the cupboard and returns the mug to the shelf of its peers.