When you get to the Halfdan's settlement, you will not find there the people you expected, but only a group of unfriendly bandits.

With the sons of Ragnar gone, bandits have claimed their old settlement for themselves. Push them out.

Unwelcome

Quest stages of Unwelcome

1. Get rid of the bandits

Just kill all the bandits.

Get rid of the bandits

2. Explore the area

More bandits might still be hiding in the remains of the longhouse,so check it.

Explore the area

Inside the building you will find two prisoners - Yanli and Rowan. You will find out from them that Sons of Ragnar left the village some time ago. Sigurd will offer them to join you and this quest will end.

Explore the area