I need to optimize the following SQL:

DECLARE @NoEntity Integer
DECLARE @Fic_Date DateTime
DECLARE @Fic_Date2 DateTime
DECLARE @First_Date DateTime

SET @NoEntity=3
SET @Fic_Date='2009-11-14 14:48:17'
SET @Fic_Date2='2009-11-15 14:48:17'
SET @First_Date='1899-12-30 00:00:00'

SELECT MAX(MitTelLogDet.Fic_Date) AS Last_Updated,MitTelLog.AI
 FROM MitTelLog (NOLOCK)
 INNER JOIN MitTelLogDet ON MitTelLog.AI=MitTelLogDet.MitTel_AI 
WHERE MitTelLog.NoEntity=@NoEntity AND MitTelLogDet.Fic_Date>=@Fic_Date
 AND MitTelLogDet.Fic_Date<=@Fic_Date2 AND
 MitTelLog.First_Date>@First_Date 
GROUP BY MitTelLog.AI

For some kind of reason, this doesn't seem to be optimized. Please, take in consideration that we have about two millions records in the main table and several millions in the child table. I need something that will work in just a few seconds as oppose to a minute.