Since their car was wrecked, they couldn't move fast. Grace offered her motorcycle to Jack. Jack was about to take her offer but he then saw it was getting dark. It was not wise to travel through unknown territory in the dark.
Furthermore, Stefan and Naomi insisted on following if Jack continued his journey. Though the two could see this fourth team didn't consider them enemies, they still didn't want to stay behind if Jack didn't stay. The motorcycle and its sidecar could only hold two people. Thus, Jack decided to stay there for the night.
He hoped Kramer and the others find a safe place for the night as well.
They went into one of the ruined houses Grace and the others had reorganized into a temporary fortress. This house had three stories.