A series of plays that's an updated and remodeled version of a classic Greek tragedy is not going to have a happy ending. Still, in a trilogy where pretty much every major character is dead by the final act, you could be expecting some serious fireworks Instead, we get Lavinia shutting herself up inside a house to die alone.
Everything just kind of grinds to a halt at the conclusion of Mourning Becomes Electra, and if you ask us, that does a whole lot to amp up the most horribly depressing parts of what is, all in all, a pretty depressing piece of theater. Lavinia's a character who's been a fighter; you might even think of her as a crusader for justice minus the cape and tights. But not anymore. By the time the play's over, she's totally crushed, and she's given up the fight. She's resigned herself to living out the rest of her days in a dark old house surrounded by ghosts, giving up any and all hopes for a happy, normal life. She's only got two things to comfort her come the end of the final Act in The Haunted. The first is the knowledge that she's punishing herself for the evil that she did: covering up murder and driving Orin to suicide. The second is knowing that whatever wicked, nasty evilness that infested the Mannon clan dies when she does, and can't ruin anybody else's life in the meantime.
The ending of Mourning Becomes Electra is O'Neill's way of suggesting that, no matter how powerful you may be, no evil goes unpunished and fate can't be escaped—and that fate springs from ourselves.