Detect Life

Drawing on your knowledge of the animating force that exists in all living beings, you can see the souls of beings present in the material plane and ethereal plane to a limited degree. Souls that exist in the material plane can be seen as long as they are within your normal range of vision. The spell is blocked by a foot of stone, dirt, or wood; 1 inch of metal; or a thin sheet of lead. Souls in the ethereal plane can only be seen out to 60ft. 

This spell bypasses invisibility and can be used to see any creature with a soul (DM's discretion), including some forms of undead.