"So, dear brother," Mycroft starts from his spot on the sofa, then breaks off. He pulls out a handkerchief and sneezes violently. John is so startled by this breach of dignity, he stares in disbelief.
"Yes?" Sherlock asks, the picture of innocence.
"You see why I-" he sneezes again. "Why I need you too-" and again.
"Sherlock," he inquires, wrapping the shreds of his pride about him, "is there a cat in here?"
"Oh!" the detective exclaims, "I quite forgot! Yes, we got a cat a few weeks ago. Why?"
"You know quite well," Mycroft says stiffly, "that I am allergic. I will be going now."
"Are you sure you won't stay for a cup of tea?" Sherlock asks pseudo-politely.
Mycroft responds witheringly, "Quite, thank you." The withering effect is, it must be admitted, rather ruined by another sneeze.
That is the last time the British Government deigns to visit their flat.