The first play in Annie Baker’s residency at Signature Theatre is now in previews there. After my exasperating experience with her Pulitzer winner The Flick, I attended with low expectations. To my great surprise, I actually enjoyed myself. The traditional crimson curtain with gold fringe covering the stage was the first sign that this was going to be something different for her. That curtain is pulled open by Georgia Engel who plays Mertis Katherine Graven, the genial innkeeper of a b&b in Gettysburg. We see the ornate sitting room with a gigantic Christmas tree and a thousand tchotchkes, stuffed animals and dolls, as well as the Parisian-themed breakfast room. Set designer Mimi Lien (Preludes, The Oldest Boy) has outdone herself. Two guests arrive — Elias Schreiber-Hoffman (Christopher Abbott of “Girls”) and Jenny Chung (Hong Chau) — a neurotic couple who have been together for a rocky three years and who have come to Gettysburg to repair the damage of a recent blow-up. From the raised voices soon after they have retreated upstairs to their room, we gather that the healing is not going well. We eventually learn why Jenny is so clingy and Elias is so mistrustful. In pain with menstrual cramps, Jenny cuts short their battlefield tour the next day while Elias goes to dinner and takes a ghost tour. Jenny and Mertis are joined by Genevieve Marduk (the wonderful Lois Smith), a blind neighbor who recounts her past brush with mental illness after she became convinced that her late husband had invaded her soul. Three times during the weekend someone asks to hear a scary story. Baker clearly had a good time developing an air of mystery and a suggestion of the imminent supernatural. There are red herrings galore including a player piano with a mind of its own, Christmas lights that turn on and off at will and a mysterious journal that Mertis keeps. What turns out to be basically a very simple story has been stretched to Baker size with three acts. Between the second and third acts, there is a unexpected treat involving Lois Smith. My only problem is that I did not find Elias and Jenny sufficiently interesting to deserve all the attention. There is no character onstage named John. I won’t reveal the reason for the title. Asta Bennie Hostetter’s costumes are fine. The clever sound design by Bray Poor involves Mertis playing CDs on a faux-antique player — Bach, more Bach and, finally, Offenbach. Director Sam Gold once again demonstrates his affinity for Baker’s sensibility. Running time: 3 hours 20 minutes including two intermissions.