You must bring all these people across the river.
BUT: the kids can't cross alone; the dad can't be left alone with the daughters without the mother's care; the mom can't be left with the sons without the father's care; the thief can't be without the police; only one adult and one kid or two adults only can use the boat at a time.
Use the mouse to click over the people you wanna put on the boat. Then click the red lever to make it work.