can't think of a good title

Mycroft: [as he hands over the case file to John] Group of men who all look very different but all seem to call themselves The Doctor or on some accounts John Smith.  Whatever their name is, these men do not seem to age despite the fact that they have this eccentric tendency of appearing in photographs, paintings, and records throughout the history of the earth.
John: A doctor?  Someone didn’t use Photoshop?
Mycroft: The Doctors.  And yes. All the photographs and paintings were obviously tested for authenticity.  Huge show-offs, these doctors.  One of them, the 7th one we’ve counted so far, appears first at President Kennedy’s assassination, and then with a family who was almost going to board the Titanic, but canceled for unknown reasons. 
Sherlock: [smiles and mutters to himself, too quiet for anyone else to notice] He would do that…
Mycroft:  Yes, they haven’t seem to have done any harm, but I’d like to keep an eye on them, just in case.
Sherlock: Don’t feel powerful enough, Mycroft?
Mycroft: [to Sherlock] Think it over.  Should be interesting enough for the both of you. [Mycroft walks out]
John: So…why’d you lie?  Again.
Sherlock: Hmm…Why not?
John: This isn’t just any case.  Men who appear throughout time and don’t age!  Even if he is your brother, how can you possibly not be interested?
[long pause]
Sherlock: He’s actually a friend of mine.  And I owe him a favor…
John: Wait, friend?  One friend- They’re all one person?  And you owe him a favor?
Sherlock: Frankly, we all owe him a favor…

(Source: starmines)