MLG MISSES APCH WHEN THEY RECEIVE A TCASII RA FROM AN ACFT THAT DOESN'T APPEAR TO EXIST.

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TURNING FINAL FOR RWY 26L AT DEN OUTSIDE ALTUR OM. WE WERE GIVEN TFC BOTH TO FOLLOW AND TO THE N. THIS IS NORMAL TO THESE PARALLEL RWYS. PRIOR TO XING ALTUR WE NOTICED TFC TO THE S ON OUR TCASII. THIS IS UNUSUAL. WE KEPT LOOKING VISUALLY FOR THE TFC AS WELL AS USING THE TCASII ON THE 5 MI SCALE. THE TFC APPEARED TO BE CONVERGING FOR A LNDG ON OUR RWY 26L. AFTER XING THE MARKER WE CONTACTED THE TWR AND WERE INFORMED THAT OUR TFC WAS ON SHORT FINAL. AS THE TARGET GOT CLOSER BOTH VERT AND HORIZ; I FLATTENED THE APCH RISING 1 DOT ABOVE THE GS. THE TARGET CONTINUED TO CONVERGE UNTIL WE GOT A TA ON THE TCASII. STILL NO VISUAL OR ATC CONFIRMATION. SEPARATION WAS BECOMING CRITICAL AND I LEVELED THE ACFT HOLDING 5800 FT MSL. WE THEN GOT AN RA ON THE TCASII AND INITIATED AN UNEVENTFUL MISSED APCH. I DON'T BELIEVE THERE WAS ACTUALLY TFC THERE. NO ONE LANDED THAT I AM AWARE OF; AND ATC DIDN'T SEEM TO BE CONCERNED ABOUT A POSSIBLE NEAR MISS ON FINAL APCH. THE TCASII IS A WONDERFUL TOOL; HOWEVER; I WONDER IF THIS WAS A 'SHADOW' OR TCASII 'ANOMALY.' WE DID HAVE PARALLEL TFC TO RWY 26R.