03 - On the Origin of Syrup | Syndicate Sequence 4 Walkthrough AC: Syndicate Guide

Use the bypassed carriage to catch up to the enemy.

Follow the carriage after starting the mission. You won't get to it on foot, but you will bypass another carriage on your way which you can hijack. This will make catching the escaping doctor much easier. Once you get close enough, it will become possible to jump on the roof of the second carriage and take it over.

Destroy the carriage in any way you want.

Once you take control of the carriage, your task is simple - scare the doctor. To do it, you must damage the carriage. Drive as fast and as bad as possible, destroying the lanterns, driving into buildings and ramming other carriages. Once you scare the doctor, stop the carriage and wait until he starts talking - this will end the mission.