Answer:
Walter's heir
Explanation:
In united states' common law, the wealth which belonged to a deceased citizens will be automatically transferred to the closest family members (the heir) , unless that person has made a legal document that specifically mentioned otherwise.
In this specific case, it does not mentioned that Walter has made a will or any prenup agreement before he died. So, Walter's share will be automatically transferred to his spouse. (in united states, spouse is considered the main heir after deceased)
