Shakespeare's story of shipwrecks, separated twins, disguise, and mistaken identity has all sorts of room for exploring the unpredictable twists and turns of romantic love. This Ten Thousand Things production of Twelfth Night, featuring an all-female cast, burrows into all the ambiguity and emerges with a trove of funny, moving treasures. We begin in the court of Orsino (Sally Wingert), a duke with a fixation on the countess Olivia (Sonja Parks). It's a jones unlikely to be satisfied, though: Since the death of her brother, Olivia has pretty much soured on any attachment to men. Until, that is, she meets Cesario (Kate Eifrig), who comes to her court to plead Orsino's case. Olivia is immediately smitten with the young emissary. The trouble is that Cesario is actually Viola, a noblewoman washed to shore after a shipwreck who has, naturally, done herself up as a guy to find employment in Orsino's circle. (To complicate matters further, she proceeds to fall in love with the duke, all the while remaining in character as a man.) Eifrig pulls off this house of cards with assurance and subtle humor. Later, she even portrays two characters at once when Viola's twin, Sebastian, finally makes his appearance. Isabell Monk O'Connor is full of knowing grins as mischievous Sir Toby Belch, Olivia's drunken uncle (at one point Sir Toby takes a leak in a bucket to one side of the stage), and Kimberly Richardson brings a weird, physical restlessness to the hapless knight Sir Andrew, who comes to Olivia's court to win her hand (but clearly should have known better). Barbara Kingsley transforms herself entirely as two different servants (one shriveled and decayed, the other ramrod straight and enormously pissy). While the plot may seem hard to follow, under Michelle Hensley's direction this production hums with clarity and precision, and by the end (after Maggie Chestovich delivers a short, sweet ballad) the trio of Eifrig, Parks, and Wingert manage to portray two romantic couples with touching elegance. This Night, which lasts a trim two hours, is full of assurance and unruly humor.