As someone who routinely deployed a scalpel, Molly Hooper probably had excellent fine motor control, but it did not extend to freehand drawing. Sherlock couldn't tell whether the rectangle she had sketched was meant to represent an aircraft carrier or a rasher of bacon.
Next to him, John leaned in intently, as if that would help. "Eraser!" he called out.
"Lipstick!" said Anderson.
"Eraser!" said Molly's brainless friend Suzanne.
Molly gave a pleading wince and turned back to the whiteboard.
"John, this is pointless," Sherlock grumbled.
"It's called being nice," John replied evenly, not glancing away from the perplexing arabesques Molly was adding.
"Yes," Sherlock ground out, "but why do I have to do it?"
"She invited us over…."
"We could have said no."
"… And you're making up for that comment about her hair." John gave a pleasant, dangerous smile. "And maybe next time, you'll think before you speak."
Lestrade snorted. "That'll be the day. "
Molly emitted a wordless squeak, and they turned back toward the newly-embellished drawing.
John frowned and squinted. "Is it a… handgun?"
"Alligator," said Lestrade dubiously.
"Idiots," Sherlock blurted, slapping his palms onto the table. "It's a bonesaw, any imbecile can see that."
Everyone turned to Molly, who looked slightly thunderstruck. "It is, actually."
"Nice work." Lestrade clapped Sherlock's shoulder. "Now it's your turn at the board."