John knows exactly what Sherlock wants by the way he walks up to him, the gait a little stumbling, the eyes a little glazed.
'P-please,' says Sherlock, a little flush of embarrassment hitting his cheeks, as it always does when things get to this juncture, 'please, can I use the toilet?'
John looks at him thoughtfully.
'How long has it been since you last went, Sherlock?'
Sherlock looks at him with perturbation, knowing what questions mean for his chances of getting to use the loo. He had asked a while ago, but John had been busy, and had said to come back later.
John isn't sure Sherlock is being entirely truthful. He's pretty sure it's been more recent than that.
'Four hours? Really?'
A look of panic comes over his friend's features, his hand pressing unconsciously against his crotch.
'Uh. Um. Maybe. T-three?'
John raises an eyebrow.
'T-three, please, John, I'm sure of it.'
John loves it when Sherlock looks as desperate as this. His cheeks are stained a pale pink, his body has an almost invisible judder from the desperation, and his breath is starting to come in short, sharp pants.
'So why do you need it so much? If it's only been three, you should be able to hold it for longer than this.'
'I – drank – a – lot – of – Diet – Coke – and – orange – juice - earlier-' stutters Sherlock, his insides starting to twist with desperation. 'T-they're diuretics. W-well, the Coke is. P-please, John, you said to come back when I needed it, and you'd let me. Please? Please?'
John grins, chewing at the corner of his mouth. He knows Sherlock is close to the edge. It's why he made him wait. He's been getting uppity about things recently, mainly because John has been too nice, letting him go to the toilet whenever he asks. He thinks the balance needs to be redressed.
'I don't think you need it enough,' he says, and Sherlock practically squeaks – if ever a man squeaked – with distress.
Sherlock only gets halfway through his latest whimpering moan of distress when it happens. John watches contentedly as the tell-tale stain spreads over Sherlock's jeans, slowly soaking the thick material, little mewls of distress coming from his mouth, sinking slowly to his knees in front of John as his bladder continues to empty, unable to take it any more.
'Tut tut,' says John, his eyes sparkling, knowing Sherlock will not be so blase in the future. 'I suppose I must have been wrong. Anyway, aren't you a bit old for little accidents?'
Sherlock thinks he might implode with humiliation. There's no going back from this, now.