Only bequests in a valid (properly signed and witnessed) will are enforceable: no other instructions as to what to do with assets after a person's death have any power whatsoever. What your father-in-law told his landlord is irrelevant: the contents of the safe deposit become the property of the estate, to be used for estate expenses and debts, and also to (if anything is left over after expenses and debts) to be distributed as per the terms of the will.The money in the box must be returned to the estate. If it is not, your wife, as executor, can file a lawsuit on behalf of the estate against the landlord and the other person, to recover the money from the box.