Something wicked this way comes. Finally. It’s been more than a decade since eclectic and eccentric Boston singer-songwriter Brian Carpenter and his cabaret-rock Beat Circus kicked off their Weird American Gothic concept-album trilogy with 2008’s Dreamland — and almost as long since they released the second part, 2009’s Boy From Black Mountain. Thankfully, this long-overdue finale more than makes up for lost time. Initially sparked when Carpenter was hired to write music for a never-produced play inspired by a true-crime book set in San Francisco’s Gold Rush era, the 15-song These Wicked Things is a fittingly theatrical (and fittingly fiendish) affair. Spoken-word tales and musical narratives of death, darkness and dashed dreams form the three rings in this twisted circus — and they’re all surrounded by a varied musical backdrop that extends from twangy desert rock and cowpunk to noirish low-rock grooves, skronking downtown jazz-punk and South American tango instrumentals. The overall vibe is a little Tom Waits, a little Stan Ridgway, a little Calexico, a little Lounge Lizards and a whole lotta freaky. Which is presumably just what Carpenter was going for. It’s hard to beat that.