The plant looks like it had a combination of too much (afternoon) sun and perhaps the heat dried the soil out as well. There is not much you can do about the sunburned leaves. You'll lose the majority of them. Just hope that the plant will grow new leaves. Keep in mind, without viable leaves, the plant can't use much water, so you want to keep the potting soil slightly moist, limiting your watering, and mist those leaves you do have. If that floor vent is blowing air at all, get the plant away from it. That forced air just dries the leaves that remain and stresses the plant even more.
Good luck.
