There are well-written film and television characters, and then there are those who are conceived with such vibrant, irresistible specificity they almost cease being merely fictional personalities on the screen. This is most definitely the case with Doris Miller, the irrepressible heroine of "Hello, My Name Is Doris." In what is the best movie role she has taken on in at least two decades, Sally Field (2014's "The Amazing Spider-Man 2") is perfection as Doris, a meek sixty-something office worker still grieving the recent loss of her mother who decides to finally start living for herself following an encounter with inspirational self-help guru Willy Williams (Peter Gallagher). As writer and director, Michael Showalter (who previously penned 2014's romantic spoof "They Came Together" and 2001's cult summer-camp satire "Wet Hot American Summer") exhibits a detectable newfound growth and maturity with this lovely, aching, frequently hilarious human study.

When her mom passes away following a long-term illness, Staten Island native Doris Miller finds herself alone in the home they shared. Having put her own life plans on hold to care for her parent, she now looks around and has little to show for her advanced years beyond the procured stuff—some of it sentimental, most of it junk—that has gradually stacked up around her house. Brother Todd (Stephen Root) and his wife, Cynthia (Wendi McLendon-Covey), want Doris to sell the property, but she cannot imagine leaving the very place where she grew up. A conversation she shares with motivational speaker Willy Williams is the catalyst which leads her to expand her proverbial wings, but it is a harmless elevator encounter she shares with handsome, much-younger new co-worker John Fremont (Max Greenfield) that awakens something further in Doris. She is easily old enough to be John's mother, but they get along so well she wonders if it makes a difference. A hopeful, long-neglected internal yearning tells Doris to take a chance, even as her search for love leads her to betray what she knows to be right.

"Hello, My Name Is Doris" excels by focusing on character nuance, truthful observation, and a whole lot of great writing. A film about people rather than glaring screenplay constructs, it offers a central heroine so sympathetic and three-dimensionally realized the viewer occasionally recoils in concern for her well-being as she steps out of her comfort zone and into a world that has practically passed her by. Doris is far from perfect, which makes her all the more real; in her ploy to get closer to John, she friend-requests him on Facebook using a fake profile and then immerses herself in the things he likes, like favorite electronic band Baby Goya and the Nuclear Winters. When she discovers he is in a relationship with down-to-earth aspiring singer Brooklyn (Beth Behrs), she is torn between liking this young woman and wanting to sabotage their romance.

Lest this seem like the setup for a "Fatal Attraction"-esque revenge thriller, it is anything but. Writer-director Michael Showalter and co-writer Laura Terruso love Doris and care about her, just as the audience does. She isn't above being a little single-minded and selfish, but for a woman who has devoted the last forty years to her mom she simply wants to make up for lost time. Likewise, despite using the occasionally dishonest or manipulative tactic to bond with John, Doris is treated with respect, understanding and an empathetic heart. It is no secret what an enormously talented, often underrated actor Sally Field is, yet there is still something revelatory about what she has accomplished with this extraordinary part of Doris Miller. Field embraces her character's every complicated facet—the loss she experiences over her mother's death; the regrets of letting love slip her by in her twenties; her fear of moving on; her struggles to not only fit in but be accepted by her younger peers; her uncontrollable romantic daydreams; her crush on the thirtyish John that turns into something deeper—giving a plucky dignity to a woman who, in less deft hands, might have been pitied or quickly become alienating. Field's every moment is either deeply poignant or very funny or both at once; hers is a masterclass performance.

As John, Max Greenfield (2014's "Veronica Mars") is warm and ingratiating, making it easy to understand what Doris sees in him. As they become friends and Doris struggles to decipher the inadvertent mixed signals he is sending out, there is discomfort, even anxiousness, at how their relationship is going to pan out. If Doris is not above a duplicitous scheme or two, we care for her so much the thought of her getting hurt is unbearable. The supporting cast is uniformly fine, but special notice goes to Stephen Root (2011's "Cedar Rapids"), bringing an affecting depth to what could have been a one-note role as Doris' brother Todd; Tyne Daly, a welcome addition as Doris' concerned best friend Roz; and Beth Behrs (TV's "2 Broke Girls"), natural and likable as John's girlfriend Brooklyn. A final scene of closure between Doris and Brooklyn is the one noticeable, albeit minor, missing piece in a script that otherwise rarely, if ever, steps wrong.

Where "Hello, My Name Is Doris" leads and how it gets there is both expected and yet not, favoring emotional honesty over banal adherences to convention. The film is tonally adept, knowing when to spring for humor and when a restrained touch is necessary. Capturing the truth of each situation, however, is Showalter's reigning priority, and he remains steadfast in seeing Doris through her arrested coming of age. Indeed, it is her cumulative growth as a person more than her desired romance that means the most by the end, though this latter question—sustained clear through to the pitch-perfect final scene—only adds to one's involvement in her journey. Like its blessedly quirky, heart-on-her-sleeve, one-of-a-kind title character, "Hello, My Name Is Doris" is beautiful and irreplaceable just as it is.