The people. The people of Israel, as distinct from the people of Judah. The particular judgment announced in Isaiah 9:11, Isaiah 9:12 is clearly to fall on them. Neither do they seek the Lord of hosts.
Israel had set itself to seek after Baal from the time of Ahab (1 Kings 16:31). The reform of Jehu (2 Kings 10:28) had gone but skin-deep. Baal was still "sought to," rather than Jehovah, when the final judgment came (2 Kings 17:16; Hosea 2:13).