The quest "The Wayward Son" is horrendously bugged.
Two problems seem to have been identified by a wide spread of users:
1. people are unable to talk to Samson - they see a quest icon over his head but no proper dialogue.
I can confirm an issue with this quest where Samson get's a stuck quest arow above his head, but will not give any quest related "cutscene dialog" - he still gives a 'you better hurry up' one-liner on activating.
Steps I took in my playthrough that triggered the issue:
- Pick up the wayward son quest from the boy's mother outside Merrill's house in the elven alienage. The quest suggests two alternate paths of action: a) ask the boys father,
ask the templar Thrask in the Gallows - Went to the boy's father (V-something), a merchant in Lowtown and pressed him for clues, he should direct the player to Samson -> Samson get's a quest arrow (both on the map and above his head)
- Talk to Samson, I threatened him to get a lead, he sends you to a warehouse in the docks -> Samson looses his quest arrow
- I traveled to the docks and entered the marked warehouse
- Then without leaving the first room and not triggering any fight I left the warehouse again
- Traveled to the Gallows and asked the templar Thrask for clues, Thrask will send you to Samson
Samson get's another quest arrow - this arrow will not disappear upon speaking to samson again, since he longer gives quest related dialog, he only repeats his 'you better hurry one-liner' - Return to the Docks warehouse and finish the quest
The 'second' quest marker for samson will stick for the remainder of the whole act, no matter if the quest is still open or completed.
I don't know if the second hint sending you to Samson triggers the stuck quest marker or if you need to actually enter the Docks warehouse as well.