Quest Stages - TG05 (Speaking With Silence)

10 Meet Mercer Frey outside Snow Veil Sanctum
I'm on my way to meet Mercer Frey at the ruins of Snow Veil Sanctum, Karliah's last known location. Together, Mercer and I intend to hunt her down and make her pay for Gallus's murder.
20 Enter Snow Veil Sanctum
35 Find Karliah
50 Speak to Karliah
200 The tables have unexpectedly turned, and Mercer Frey has been revealed as Gallus's killer. I now find myself in Karliah's care after Mercer tried to murder me, claiming I'd outlasted my usefulness by witnessing their conversation. I've also discovered that Mercer, Gallus and Karliah were members of some sort of group calling themselves "The Nightingales" - guardians in service to the goddess Nocturnal. What they're protecting or what this has to do with the Guild is still a mystery to me.