Deadly Crossing is a secondary quest that is available as you explore Velen and Novigrad during Act I.
Name: Troll Bridge
Expect to encounter bandits at the bridges and river crossings across Velen. They have set up tolls for passengers, and you will have three ways of dealing with the lawless brutes.
Following contains quest spoilers. You’ve been warned
Troll Bridge toll
When you go to the Troll Bridge marker on your map, you will be asked by the bandits guarding it to pay a toll in order to go across.