On The Orville Season 2 Episode 13, an accidental time distortion brings Grayson from before her relationship with Mercer onto the Orville, causing all sorts of confusion
Mercer and Grayson reminisce about their life together before the Orville and Mercer proposes trying a relationship again and Grayson turns him down again.
A device that LaMarr and Isaac are working on holds the potential for time travel. When a gravitational wave hits the ship, Grayson is standing closest to the device. She leaves the room but then Isaac turns around and finds another version of Grayson standing in the lab.
The new Grayson is from seven years previous, just after her first date with Mercer. As Isaac and LaMarr have no way to send her back to her time, she settles into life on board the ship as a lieutenant, the rank Grayson had seven years ago.
She and Present Grayson butt heads over the information she discloses to her shipmates as the commander would like to be discrete about some of her activities. Lt. Grayson also pursues a relationship with Mercer which both Cmdr. Grayson and Malloy warn against.
Kaylon ships are detected but avoided.
When Lt. Grayson tries to get intimate, Mercer balks at the strangeness of it. Just then the Kaylon ships are detected again and everyone is called to the bridge.
Lt. Grayson joins them on the bridge and suggests a plan to evade the Kaylons and it works.
Once safely away, she and Cmdr. Grayson make peace. Isaac and LaMarr come up with a way to send her back. They propose a memory wipe to ensure she doesn't change Cmdr. Grayson past.
The procedure taxes the Orville's engine for the power required but they manage to send her back to her time. When Mercer calls her up for a second date, she declines and hangs up on him, changing Grayson's history considerably.
On The Orville Season 2 Episode 13, a time distortion has knock-on effects on the relationship between Commander Grayson and Captain Mercer.