CL65 DSNDED THROUGH ASSIGNED ALT AND CONFLICTED WITH AN L188 AT FL210 DSNDING TO FL190.

Narrative

ACFT #1 WAS CLRED FROM FL240 TO FL220. PLT READ BACK FL270 I NOTICED ACFT #2 PASSING THROUGH FL217. I ASKED TO 'VERIFY' AT FL220. PLT SAID 'NO; WE'RE GOING TO FL200.' I CLBED ACFT #1 BACK UP TO FL220 AND DSNDED OTHER ACFT (ACFT #2) FROM FL210 TO FL190. I TOLD BOTH ACFT TO EXPEDITE. ACFT #1 SAID HE SAW ACFT #2. ACFT #1 NEVER MENTIONED ANYTHING ABOUT ANY TCASII ALERT. SUPPLEMENTAL INFO FROM ACN 593350: WE WERE ON THE TARNE 2 ARR INTO CINCINNATI AT FL240. WE WERE TOLD TO DSND TO FL200 AND THE CAPT; THE PNF; REPEATED THIS AND THEN CONFIRMED WITH ME AND SET FL200 IN THE ALT PRESELECTOR. PASSING THROUGH ABOUT FL210; THE CTLR QUERIED IF WE WERE LEVELING AT FL220. THE CAPT RESPONDED NO; THAT WE WERE DSNDING TO FL200. THE CTLR THEN TOLD US TO DISCONTINUE DSCNT AND CLB IMMEDIATELY UP TO FL220. AT ABOUT THIS TIME WE RECEIVED A TA ON THE TCASII. THE CTLR TOLD US ABOUT TFC AHEAD AND WE RPTED THAT WE HAD THE TFC IN SIGHT. WE IMMEDIATELY BEGAN A CLB UP TO AND LEVELED AT FL220. WE DID NOT RECEIVE AN RA AND WE DID NOT HEAR ANYTHING ELSE FROM THE CTLR ABOUT THE INCIDENT. I BELIEVE THAT I HEARD THE CTLR CLR US TO DSND TO FL200 AND MY CAPT BELIEVES THAT HE HEARD THE SAME THING.