Mo. Rev. Stat. § 525.130: Plaintiff may exhibit interrogatories against garnishees — interrogatories, when filed.

The plaintiff may exhibit in the cause written interrogatories touching the property, effects and credits attached in the hands of any garnishee, and require such garnishee to make full, direct and true answers to the same, upon oath; which interrogatories shall be filed at the return term of the writ, and within the first three days thereof, if the term shall so long continue, and if not, then before the end of the term, and not afterward, unless for good cause shown the court shall order otherwise.