Watson relaxed in the tub. The warm water felt marvellous on his sore muscles and bruised arm. Holmes should be at Scotland Yard for at least another hour; such guaranteed privacy was a rare luxury. Watson had collected the dirty laundry from his own bedroom as well as Holmes'. Later he would bring it all downstairs as he helped Mrs Hudson empty the bath of water. His actions were courteous and, and efficient. Nothing indecent about it.
Watson sat up in the tub and reached for the pile of clothing. He sorted through it, heart already pounding and prick hardening under the water, until he found Holmes' undergarments. He inspected them carefully. No sign of blood. That was good. Holmes had a habit of concealing injuries from his physician. Very good. He closed his eyes and brought the fabric to his face. Felt the thin linen brush against his moustache. The odour was distinctly masculine, reminiscent of boxing clubs and barracks and Holmes. Watson swallowed, throat clicking, and allowed his hand to stroke down his body, under the water to where he needed it.
The door banged open. "Ah, there you are, Watson," said Holmes.
Watson dropped the smalls and pushed them under the water, as if that might somehow conceal both it, and his engorged organ. "I wasn't –"
"Engaging in a bout of onanism whilst sniffing my drawers?" Holmes finished, his eyes darting quickly around the room before settling most intently on the man laying naked in the tub.
Watson felt his face heat. His prick, far from discouraged by the attention, stiffened further under the wet fabric. "I'm not –" Watson began, and then halted, miserably unsure of how to salvage the situation. Holmes would detect any lie in an instant.
"I perceive you are concerned about my reaction. There's no need. Nothing shocks me. I'm a scientist, old boy. And this?" Holmes raised an eyebrow at him. "Is an experiment. I'm quite pleased to see you practicing my methods. However, I suspect you would benefit from my guidance in exploring your hypothesis." Holmes closed the door firmly behind him and locked it.
"I am a strict empiricist, Watson," Holmes said, unbuttoning his waistcoat and tossing it onto the pile of laundry. "And I therefore believe that all knowledge is derived from," he licked his lips and continued in a murmur, "sensory experience."
Watson found himself in a state of fervent agreement.