The professor didn't expect that his momentary compassion would cause such big trouble.
That kid has the destructive power and brains of a troll.
But there was no way the professor could treat that child like a Gryffindor.
Once he wanted to be angry, those green eyes would look at him with watery eyes, full of dependence, and his little milk-scented hands would open up for a hug, calling out to Severus softly and waxily.
The professor had a cold face but gently picked up the child and said to the child for the umpteenth time: "Call me professor."