A 47-year-old man had to undergo a four-hour, life-saving operation after being stabbed at his home in Billingham.
Police said the attacker walked into the man's house in South View, Billingham, on Saturday night, stabbed him once in the stomach, then fled.
The man's teenage daughter was in the house at the time of the attack, but was unharmed.
Cleveland Police said the motive for the attack was a "mystery" and appealed for information.
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