This, boys and girls, is a crack (or two) in a lath and plaster wall. You may have to enlarge the photograph to get a good look. (There is also a shadow from the chandelier to complicate things)
Here is the lesson.
When renovating an older home containing lath and plaster walls remove all the lath and plaster. Take it down to the studs. Be ruthless. Saving some walls in their original state will not save you any significant time or money.
There are two places in this house that have the original L&P; the hallway and one wall in the kitchen. There are two places in this house with cracks in the walls; the hallway and one wall in the kitchen. This picture was taken of the door to the sunroom. There are more cracks on the other corner and a fine one above the door to the living room.
Fixing this is going to cause a big mess. If it ever happens.
Need I say more?