The Best Episodes Written By Aaron Helbing

The death of the Knights Templar Order is imminent as Landry and his Templar brothers are sentenced to burn at the stake.

Mark Mardon, having survived his apparent death during the black-matter explosion, returns seeking revenge on Joe for the death of his brother Clyde... and has the same weather-manipulation powers as his deceased sibling.

When Harrison activates the particle accelerator, the team has no choice but to evacuate the five metahuman prisoners. Unfortunately, with time running out, Barry has no choice but to turn to Captain Cold for help. Meanwhile, Eddie escapes but has some surprising news for Iris.

In an ironic twist of fate, a gladiator from the house of Batiatus will stand in the way of Spartacus trying to free Crixus from Roman captivity. Ilithyia's scheming puts her marriage to Glaber at risk.

Barry enjoys the annual tradition of tree trimming and gift exchange with Joe and Iris. He gives Iris a touching gift, but the moment is interrupted by Eddie’s arrival.

Vandal Savage arrives in Central City and sets his sights on Kendra Saunders. After Vandal attacks Kendra and Cisco, they turn to Barry for help. Realizing how dangerous Vandal is, Barry takes Kendra to Star City and asks Oliver and team to hide her until he can figure out how to stop Vandal. However, things quickly go from bad to worse when a man with wings AKA Hawkman shows up and flies off with Kendra. Meanwhile, Harrison develops a serum to make Barry run faster and asks Jay to test it out. The crossover continues on Arrow S04E08 Legends of Yesterday (II).

Landry reunites with his daughter, only to be separated once again. Growing impatient with DeNogaret’s legal strategy, King Philip prepares his army for war. Margaret discovers one of Prince Louis’ dark secrets.

Banished from the Knights Templar after the discovery of his affair with Queen Joan, Landry must work to redeem himself under the watchful eye of a mysterious veteran of the Crusades. King Philip formulates a plan to take action against the Templars, while dealing with the return of his erratic, eldest son, Prince Louis.

When aliens called the Dominators attack Central City, Barry speeds over to Star City to ask the Green Arrow for help in stopping them. Realizing the battle against the Dominators is bigger than they thought, they track down the Legends of Tomorrow, and Barry and Cisco create a breach to bring back a secret weapon – Supergirl. Once all of the super friends are assembled, they come up with a plan to attack but a shocking secret related to Flashpoint is revealed and suddenly no one is sure who they can trust. Meanwhile, Wally wants to join the battle against the aliens but Iris tells him he’s not ready. The crossover starts on Supergirl S02E08 Medusa (I). It continues on Arrow S05E08 Invasion! (III) and DC's Legends of Tomorrow S02E07 Invasion! (IV).

On Earth-2, the team races to find Zoom's lair and asks for help from the most unexpected source. Meanwhile, back on Earth-1, Caitlin rushes to perfect Velocity-9 so that Jay can stop the Geomancer.

After Zoom reveals his true plan, Barry vows to do whatever it takes to stop him.

Batiatus purchases a fresh batch of slaves during an auction to be trained as gladiators and ponders the idea of selling Crixus.

With Alchemy and Savitar still looming threats, Barry is unable to focus on the Christmas holiday, and especially his relationship with Iris. Determined to stop Savitar, Barry goes to Earth-3 to get advice from Jay Garrick. Wally wants to help Barry fight Savitar and reveals that he’s been training with H.R, which doesn’t go over well with Barry. As Cisco faces his first Christmas without his brother Dante, old wounds are reopened.

After the shocking revelation that Zoom is Jay Garrick, Barry is more determined than ever to get back to Earth-2 to stop Zoom forever. Desperate to find a way to increase his speed, Barry decides to travel back in time and masquerade as his earlier self in order to get his arch-nemesis, Dr. Harrison Wells/Eobard Thawne, to teach him how to run faster. However, things don’t go as planned and Barry is stunned to face familiar foe Hartley Rathaway, as well as old friend Eddie Thawne. Iris makes peace with her past in order to embrace her future.

Spartacus leads a daring assault to provide food and shelter for his people. Crassus builds a fearsome army and receives an unexpected visitor.

Pete Ross returns to town and finds a number of surprising changes since his departure. Besides resolving his feelings toward Clark since he learned of his friend's secret, Pete has to deal with the acquisition of a superpower of his own.

Jay Garrick, a mysterious man from Earth-2, appears at S.T.A.R. Labs with a dire warning about an evil speedster named Zoom, who is set on destroying The Flash. Barry and the team must decide if they can trust this stranger even as they face yet another powerful meta-human. Meanwhile, Joe must deal with a determined officer named Patty Spivot who wants to join his meta-human task force.

Having performed shamefully in the arena against Crixus, Spartacus is forced to fight in the Pits. Batiatus, determined to profit from Spartacus, may be at risk if his debts aren't repaid.

After learning about Bruno and Peia, Clark works to reignite Lois' interest in taking Bruno down; elsewhere, Natalie meets Matteo's parents, with disastrous consequences.

When Cisco gets a vibe of Eobard Thawne, Barry and the team don’t believe it. But, after an attack at Mercury Labs, Christina McGee confirms that the Reverse Flash is back. Meanwhile, Iris and Francine share a nice moment that brings Iris closer to her brother, Wally.

After a bomb explodes downtown, the army rolls in and takes over. When Joe learns Iris is writing about 'The Streak' and tries unsuccessfully to have the story stopped, Barry decides to have The Flash pay her a visit.

Miranda endeavors to save the island. Eleanor sees old wounds reopened. Rackham is on the scent of a secret. Vane is forced to take matters into his own hands.

Caitlin takes Barry out to a local karaoke bar to help them both find new loves. Caitlin strikes out but Barry meets a sports reporter and asks her out for a date. Meanwhile, Cisco considers Hartley's dangerous offer; and the team search for Shawna, a meta-human with teleportation powers who just busted her boyfriend out of Iron Heights.

Grodd returns to Central City and kidnaps Caitlin. Barry and team race to find her before it’s too late. Meanwhile, Cisco plans his first date with the new barista at Jitters, Kendra Saunders and Patty begins to suspect Barry is hiding something from her.

When Jesse Quick informs the team that her father has been abducted, Barry, Caitlin, Cisco and Julian voyage to Earth-2 on a rescue mission to save Harry from Gorilla City. As they trek through the forest, Barry and the team are immediately captured and brought to Grodd. Grodd tells them he needs their help to stop Solovar, the leader of Gorilla City, as Solovar wants to invade Earth-1. Meanwhile, back on Earth-1, Jesse and Kid Flash hit the streets to stop a metahuman that can control gravity, with H.R. and Joe guiding them from S.T.A.R. Labs.