Eliza Harmon, also known as Trajectory was a scientist for Mercury Labs. She was also a former colleague of Caitlin Snow when the latter worked at Mercury Labs for a few months, after the death of Ronnie Raymond.
Caitlin and Eliza used to work closely in the months after the singularity appeared over Central City. After Caitlin returned back to S.T.A.R. Labs she had trouble formatting the extracellular matrix for the velocity-9 intended for Jay Garrick, so she went to Eliza for help. Caitlin followed the rules for information compartmentalization and only gave Eliza three of the eight components necessary to create the speed drug. Eliza however, reverse engineered it, successfully turning her into a speedster, at least until the drugs ran out. She quickly became addicted though, and much like regular drug addicts, started falling apart and relying on the Velocity-9. She ran around Central City, usually at night, in a suit she created for herself to wreak havoc and steal items from people. This led to people believing the red streak they saw was The Flash, who appeared to now be a 'petty thief'. She named herself "Trajectory", and attacked S.T.A.R Labs, locking Barry in the pipeline before he knew what was happening. Trajectory then forced Team Flash to create more velocity-9 for her (as at this point she had run out) at the threat of killing Jesse Quick, Harrison Wells' daughter. They gave Eliza the drug, and as a test she stabbed one of the vials into Jesse to make sure there weren't any sedatives inside. Once she was sure the velocity-9 was safe, she sped off to Central City bridge to cause more chaos. Cisco released Barry from the pipeline and he was able to apprehend Eliza, until she took more of the drug and ran off. This time though, she ran too quickly and her lightning turned blue just before she dissapeared from reality, possibly into the Speed Force.
- Eliza is the first lady speedster to ever appear on The Flash, and is currently the only one.