Dr. Watson is currently on a call. Holmes called him from the residence of his current client, borrowing their telephone to update Watson on the case he is handling

"Ah yes, very genius of you, but must i remind you of how reckless that is?! Please, for the love of God, lessen your impulses, Holmes!"

He frowns while smoking a cigarette, his other hand holding a book he was about to read while lounging on a sofa back at 221b Baker Street before the call, he wore a red wrap robe & some comfy pants since he's on his day off

Watson is about to go mother hen mode & scold more, but a knock on the door alerts him