- Speak with Gabriella in the Dark Brotherhood Sanctuary.
- Travel to Dragon Bridge.
- (Optional) Steal Gaius Maro’s travel schedule.
- Kill Gaius Maro and plant the Incriminating Note. For a bonus, kill him in a major city.
First, you will be instructed to speak to Gabriella inside the Sanctuary. She will give you your mission – you are to kill the son of Commander Maro, Gaius Maro and plant a letter framing him for the plot against the Emperor. Killing him in a city other than Dragon Bridge will grant you a “reading of your future,” according to Gabriella, but this is optional.
Travel to Dragon’s Bridge first, and if you choose, steal Gaius’ travel schedule. This makes things much easier, and you really have no reason not to do it – simply sneak into the building the schedule is in and nab it. Once outside, check what day of the week it is in game, then read the schedule and travel to the appropriate city that matches up.
This is the schedule as it appears in game that you steal from the Pentius Oculatus Outpost:
|Morndas||Solitude, the Emperor’s Tower||–|
|Morndas evening||Solitude, Castle Dour||Food and sleep.|
|Tirdas||Windhelm, the Palace of the Kings||–|
|Tirdas evening||Windhelm, Barracks||Food and sleep.|
|Middas||Riften, Mistveil Keep||–|
|Turdas evening||Whiterun, the Bannered Mare||Food and sleep.|
|Fredas||Markarth, Understone Keep||–|
|Fredas evening||Markarth, guard tower||Food and sleep.|
|Loredas||–||To be spent at your discretion.|
|Sundas||–||To be spent at your discretion.|
Don’t be afraid to simply wait for another day. There is no time limit on this quest and when he has completed his schedule he will repeat the same schedule next week. It is much easier to assassinate him on the road when he is alone, but you forfeit your bonus reward by doing so.
Wherever you kill him, loot his corpse and plant the Incriminating Note on his body, then return to the Sanctuary. Alternatively you can reverse-pickpocket the note prior to killing him.
You will be rewarded with leveled gold. If Gaius died in a city, you will also receive Olava’s Token. The token will give you a miscellaneous quest to find an “assassin of old,” which will lead you to a dead Dark Brotherhood member in a cave dressed with an upgraded version of every piece of Dark Brotherhood armor.
Note: If you complete the Stormcloaks questline, Dragon Bridge will be filled with Stormcloak Soldiers who will attack Gaius and his father on sight. However, they appear to be un-killable until they finish their conversation, so they will wipe out the local Stormcloaks, but they will also be hostile to the player, but only as long as they are being attacked by the Stormcloaks.