SPOILER ALERT: This article contains details about the Arrow-Supergirl-The Flash DC crossover event.

How tough is Gotham City on tourists? That’s the lesson that awaits three out-of-town superheroes — Green Arrow, Supergirl and the Flash — as they (and The CW network) all test their luck in Batman’s hometown in a three-night superhero crossover event that begins tonight on The Flash (8 EST/PST).

The CW has made an annual tradition of these epic crossover events and this year’s edition brings together the title heroes from three of the network’s five live-action DC Comics franchises. The crossover event also has a second, grander ambition: it’s intended to launch a sixth DC series for the network by introducing Gotham City’s notoriously fierce Caped Crusader to The CW roster of heroes.

There’s just one thing: “That’s not Batman,” the Flash (Grant Gustin) says in tonight’s episode when the mysterious masked vigilante who calls herself Batwoman arrives on screen with a scowl. The black-and-red-clad crimefighter is portrayed by Orange is the New Black actress Ruby Rose, whose casting made headlines around the world.

Among the reasons for the coverage: If The CW launches Batwoman next fall as expected, Rose would be the first openly gay or lesbian lead in a DC or Marvel superhero adaptation (feature film or television series). The Batwoman character is also the most prominent gay or lesbian character in the the eight-decade history of DC Comics. Rose has said the role represents a “childhood dream” come true.

Batwoman is secretly Kate Kane, cousin of Bruce Wayne. Tonight’s episode reveals that three years have passed since both Wayne and Batman left Gotham without explanation. As the Dark Knight’s substitute, Batwoman has her hands full in a city spiraling into crime and chaos.

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Rose is a compelling presence on screen in her costume (which is extremely faithful to the comics) although her action sequences seemed clipped and constrained, which may suggest that her elaborate ensemble (with mask, flowing cape, a long wig, utility belt, etc.) may be an early challenge she must overcome. Rose’s best work in the first-night episode is in her civilian identity, Kate Kane, whose dark charisma and calculating gaze make her pitch-perfect as a believable relative of the obsessive Batman.

The no-nonsence intensity of Batwoman works well in tonight’s episode, too, which has plenty of humor opportunities thanks to its playful plot device: a Freaky Friday-style body-switch between the Flash and Green Arrow (Steven Amell) which gets major mileage out of the polar-opposite personalties of the grumpy bowman from Star City and the sunny speedster from Central City.

Bickering, sparring and mocking each other, Gustin and Amell deliver great performances as the transposed heroes. Both display sharp timing which suits their roles as a supernaturally accurate marksman and the “Fastest Man Alive.”

The pair seek out a friend to help them solve their identity crisis: Supergirl (Melissa Benoist), who is hanging out in Smallville with her cousin, Clark Kent (Tyler Hoechlin), and Lois Lane (Elizabeth Tulloch). Then it’s off to Gotham City, where clues lead the trio to Arkham Asylum, where a reality-bending threat may erase them from reality — unless the inmate riot kills them first.

The three-part story “Elseworlds” continues Monday night with Arrow and concludes on Tuesday on Supergirl, which this week traded its usual Sunday night slot with The Flash. Only the first two installments of the crossover event were made available by The CW for this review..

The episodes are loaded with Easter eggs and gags that wink at the television history of DC Comics adaptations with sights, sounds, cameos and references that should delight diehard fans but don’t distract newcomers to the DC mythology. There’s a lot to see in the trilogy-in-tights and, with Rose as Batwoman, a strong signal that Gotham will be a city without limits and the next branch office of The CW’s Arrowverse.