Acquisition
You will only be offered this quest (by a letter in Gamlen's House), if you have completed all main plot quests in Act I. It serves to continue the story even if you don't have the 50 sovereigns to pay for The Deep Roads Expedition.
Walkthrough
Meet Dougal near the foundries in Lowtown at night.
Dougal offers to finance your part of The Deep Roads Expedition. In return he asks for double his coin when you return from the expedition.
If you refuse he will peacefully wait around in case you change your mind.
Aveline: rivalry (+5) if you accept the offer.
Carver: friendship (+5) if you accept the offer.
Rewards
* This quest is there in case Hawke has spent too much to be able to finance the expedition after having done all the other quests. If you accept, the money will be sent to Bartrand so that you can continue the plot. When you return he will confront you, asking for an additional 100 gold. You then have the choice of either paying up or refusing; refusing will result in fighting him.
Notes
This quest also appears if you already have enough money for the expedition.