Mo. Rev. Stat. § 516.240

If any action is commenced within the time prescribed in sections 516.010 to 516.230, and the defendant in the suit dies before judgment, and if the right of action is such as survives against the representatives of the defendant, the plaintiff may commence a new action against the heirs, devisees or assigns of the defendant, as the case requires, within one year after his death; but if an executor or administrator is appointed then the new action may be commenced against the executor or administrator within nine months after the first published notice of letters testamentary or of administration whether more or less than one year after such death.