Complex sentence: Sobinski by now assumes that Maria will leave her husband, give up acting, and come live with him on a farm, but before she can explain that she only wanted a casual fling, her maid rushes in, saying Germany has declared war on Poland.
Split into simpler sentences: Sobinski by now assumes that Maria will leave her husband, give up acting, and come live with him on a farm. Before Maria can finish putting him right, her maid rushes in, saying Germany has declared war on Poland.