Mo. Rev. Stat. § 140.560
Every person holding a lien upon any real estate in this state by virtue of any illegal or invalid tax deed, shall, upon the payment or tender to him by the owner or any person having an interest in such real estate, of the full amount of said lien, together with the sum of one dollar and twenty-five cents, and together with any sum that may be due him as an occupying claimant, make, execute and acknowledge before some officer authorized to take acknowledgment of deeds, and deliver to the person making such payment or tender a deed of release, releasing to the owner of such real estate all claims the holder of such invalid tax deed has on such real estate on account of such tax deed; and upon the failure of the holder of such lien to execute such deed of release as herein provided for, after demand, he shall be subject to an action in any court of competent jurisdiction to quiet the title of such real estate as against such lien, in favor of the person making such payment or tender, and shall be liable in said action for all costs accruing therein including a reasonable fee for the plaintiff's attorney in such action.
§ 140.560, RSMo