No one except Sherlock was surprised when, more or less the moment this particular perfidious criminal was taken into the custody of Scotland Yard, Sherlock fell extremely ill.
"Exhaustion," John had snapped, "a broken arm, a gunshot wound - you should be grateful your heart hasn't decided to give up under the strain." He had then dosed Sherlock liberally with medicines designed to make him sleep (and it had to be liberal, he had complained to Mary later, because the idiot used many of the ingredients recreationally and so had built up an irritating tolerance), all the while complaining about the stubbornness of fools.
Then Mary had sent him to sleep, lest lack of rest bring him down with the same fever. He'd argued only a little.
Mary didn't actually mind playing nurse. She didn't enjoy it, but there were worse occupations - arranging funerals, for instance - and if she did it, she could at least be certain that those she cared about were properly looked after.
In Sherlock's case, that meant providing him with a great many things to read.
At this point, Mary didn't think Sherlock was actually capable of resting - at least, not all of him, all at once. If his body wasn't occupied, his mind had to be, and if his mind was not occupied God forbid his body be idle, lest he explode and do damage to himself and to others.
When she brought in tea with a new book on the fauna of South America, Sherlock had already begun to seethe quietly in his window-seat. As she came in, he growled, "This is completely unnecessary."
"Doctor's orders," Mary replied sweetly, and received a glare that might have lit her on fire.
"I'm nearly inclined to seek a second opinion," Sherlock retorted, but then lost some time to a horrific bout of coughing while Mary put the tea down on the small table beside him and the book in his lap.
"I wouldn't," she said, when he could possibly hear her again. She sat down by his feet. "You might end up in a hospital somewhere with nurses looking in on you every ten minutes. And then you'd eventually commit the murder of some inoffensive doctor and then we'd be forever deprived of your charming company."
She reached forward to put her wrist against his forehead, checking on the fever; Sherlock jerked his head away, exactly like a sullen child. Mary tried not to smile at him. She did actually understand the intense discomfort of enforced idleness, but there wasn't anything that could be done. His lungs were badly congested, the fever kept returning and whether he would admit it or not, if he tried to walk much farther than the water-closet he'd collapse in the middle of the floor.
So Mary leaned over and kissed his forehead instead, which he submitted to with only a bad-tempered noise as he flicked the new book open and began to submit the pages to the warfare he called reading.