As immersive, progressive performance experiences go, you aren't going to find much that isn't fun and cool about the Boxcar Theatre's latest, highly ambitious offsite project, The Speakeasy. It's a fully realized, choose-your-own adventure evening in which you could potentially get very wasted at the bar, lose $100 in fake money at the casino, and watch as the semi-tragic lives of a couple dozen 1920s-era nightlife dwellers play out around you.

As we earlier described when the piece was about to begin previews — they have, probably wisely, kept the critics at bay for over a month while they worked out the kinks in this extremely complicated, multi-room production — The Speakeasy is part ensemble theater, part live-action video game, part cabaret act, part improv, and part living museum in the style of Old Sturbridge Village or Colonial Willamsburg. Each night, after rendezvous-ing with guides in Civic Center, audience members (many of whom elect to dress in 20s-era clothing) are given maps to the secret location of The Speakeasy on one of the Tenderloin's sketchier blocks. One entrance is concealed behind a storefront that says Joe's Clock Shop, and you need to go through a side workshop and a secret door to get back to the door of the bar, which requires a secret knock — the other entrance, where half of guests will enter each night, is via a back alley and takes you into the cabaret.

The multi-dimensional piece doesn't function like a play, and there is no specific beginning or structure. Audience members are encouraged to create their own experience and wander at will after the first portion of each evening begins in the bar or cabaret, which means that no one can see everything that occurs in a single visit, encouraging return visits for those who enjoy it.

As director/creator Nick Olivero sums it up: "Thirty-five actors inhabit the space and it is up to the audience to decide what they want to see. Throughout the night patrons may encounter flappers and floozies, business men trying to start a doomed bootlegging operation, couples both older and younger working through their marital problems, a novelist seeking inspiration, a degenerate gambler who brings his little girl to the bar, a bouncer with a heart of gold, the club owner who's been having an affair, World War I vets, and more."

I saw much of that, and since the stories only barely intertwine or particularly affect one another, I did not feel like I had missed much until I talked to a couple of other people who saw a bunch of other things I wish I'd seen — there is definitely room for some FOMO here. For $5 you can get (adjusted for inflation) $137 in gambling chips, and you can retreat to play craps, roulette, or blackjack whenever you feel like it, which I did at least twice until I lost it all. Cocktails are $10 and very free-flowing via the bartender or a gaggle of uniformed waitresses, and they've come up with a clean way of processing payment by taking credit cards in envelopes at the outset, and giving you numbered tokens that you use as your tab the rest of the night.

One of the most effective pieces in the evening was a musical number, performed in the bar, that doubled as a flash-forward sequence for ten or so cast members talking about how they were impacted by the stock market crash of 1929, all set to the song "Brother Can You Spare a Dime." Period music is used to great effect throughout the evening, via a house band on a platform over the cabaret stage, a talented pianist, several talented male and female singers, and a player piano in bar. A favorite line figures in the cabaret when, at one point, an older married woman says to a younger one, "Your generation has the best music."

Another favorite moment: The MC, on stage in the cabaret with a flask in his hand, talking about how "90 years no one may remember us," before he leads the room in a round of "Those Were the Days."

Technically, also, the thing is quite a feat. The set, involving five rooms and the dual-level cabaret, was beautifully executed, and a group of stage managers and light and sound operators controlled a massive number of light cues throughout the space in a hidden control room, somewhere, via hidden cameras, without any flubs that I could see.

There are moments in which the scripted dialogue feels forced or clichéd, and others where the history-lesson aspects feel unnecessarily didactic — I wanted it to be more theater and less Colonial Williamsburg whenever possible, and this did occur during a stirring and experimental moment involving some shellshocked WWI vets and gas masks, and at several other points.

Regardless, the experience already seems to be a hit with twentysomethings seeking out a unique blend of entertainment, costuming, and boozing. At certain points after 9 p.m., as people get drunker, there will probably always be the risk that audience members get loud or disruptive, but the performers all seem to know how to handle this, not the least of which is telling people they need to "speak easy."

I would recommend opening the envelope of special tips, which is given to you with the caveat that you don't have to look at it if you don't want to, only because it will probably help you to see a few of the more notable vignettes and numbers. And I'd recommend snagging a reservation that gets you into the bar area first, but I'm not sure how they're dividing those up — entry times are staggered between 7:30 and 8:00 p.m., and I was told to arrive at 7:50 p.m. That's the other thing, you should be on time, as the logistics of this thing are complicated enough without people arriving late.

All told, Olivera and his Boxcar ensemble have pulled off an innovative and impressive piece of theater that's unlike anything I've seen in the Bay Area, and it's likely to be a lasting hit, if I to guess, for that very reason. It's also great to see something like this mounted in a time of economic boom in San Francisco when the arts don't often enough get the patronage they deserve here — and Olivero was canny enough to find some techie investors to create something that will, very clearly, appeal to a young audience.

The Speakeasy is playing at a location that will be disclosed to you once you've made a reservation and appeared. Reservations are $60, made only online, and you can reserve a table in the cabaret for $10 more. Cocktails and casino chips are separate, and no, you can't win any real money. For patrons who have attended the show, there is an after-hours club they've dubbed Club 1923, and for $10 more you can hang out after the show to drink and gamble. The show runs about three hours.