Danny is the assistant to Allen Lygon, he was hired about a year or 2 before the incident that resulted in Almiras (my version of steamheart/the listener) death.
During the year she was dead, Danny worked with Allen to keep Roberts tracks covered and showed that Almiras death wasn't an accident. He collected evidence against Robert before others could get it, bribed, blackmailed, and stole. He grew up in the streets so he applied the skills he used to survive to keep Robert and Almira safe.
When the Citadel found him and Allen, Danny chose to stay in the fire and even told Allen "I'd rather die here with you than leave and live as a coward."