The twisted chain stitch is a variation of chain stitch with crossed loop. Unlike chain stitch the twisted chain stitch is worked above the adjoining stitch to create a twisting effect.
Bring the needle up at 'a' and go down at 'b' then angle the needle at 'c' pass the working thread over and then under the needle to form a closed loop as you pull through. Continue the pattern till the end of the row and secure the stitch at the end.