The action of the play centers around two relationships: Myrtle and Lucinda, who are in love, and Bevil and Indiana, who are in love. Unfortunately, Lucinda's father has engaged her to Bevil with the approval of his father. Meanwhile, he's taking care of Indiana—who has lost her family—and trying to help his friend Myrtle marry Lucinda. Bevil says:

But what a day have I to go through! to put on an easy look with an aching heart! If this lady my father urges me to marry should not refuse me, my dilemma is insupportable. But why should I fear it? Is not she in equal distress with me? Has not the letter I have sent her this morning confessed my inclination to another? Nay, have I not moral assurances of her engagements, too, to my friend Myrtle? It's impossible but she must give in to it; for, sure, to be denied is a favour any man may pretend to. It must be so—Well, then, with the assurance of being rejected, I think I may confidently say to my father, I am ready to marry her. Then let me resolve upon, what I am not very good at, though it is an honest dissimulation.

It's a tangled web because Bevil isn't willing to tell Indiana how much he loves her until things are worked out with his father. He doesn't feel it's right to do so; however, Indiana isn't sure of his feelings. Lucinda is also close to being engaged to another man if her engagement with Bevil ends—a rich, strange man who doesn't love her.

To make things even more complicated, Myrtle isn't sure that Bevil can really be trusted. Things are so complicated that he can't trust his friend and actually engages him in a duel. Richard Steele writes:

Myrtle: Mr. Bevil, I must tell you, this coolness, this gravity, this show of conscience, shall never cheat me of my mistress. You have, indeed, the best excuse for life, the hopes of possessing Lucinda. But consider, sir, I have as much reason to be weary of it, if I am to lose her; and my first attempt to recover her shall be to let her see the dauntless man who is to be her guardian and protector.

Bevil: Sir, show me but the least glimpse of argument, that I am authorised, by my own hand, to vindicate any lawless insult of this nature, and I will show thee—to chastise thee hardly deserves the name of courage—slight, inconsiderate man!—There is, Mr. Myrtle, no such terror in quick anger; and you shall, you know not why, be cool, as you have, you know not why, been warm.

Luckily, Bevil is smart enough once he calms down to stop the duel from going forward. He reassures Myrtle that he doesn't love Lucinda and proves it by showing him a letter from Lucinda that proves he's only trying to help. Only with his cleverness and kindness are events able to happily proceed.

Ultimately, the characters are able to marry who they want because of a pleasant surprise: Indiana's lost father is actually Lucinda's father as well. None of them knew the other was related until they meet. He's happy to have his daughter back and splits his fortune between the two girls. The rich man who claimed to want to marry Lucinda withdraws his suit because he really wanted the money. Steele writes:

Cimberton: I hope, sir, your lady has concealed nothing from me?

Mr. Sealand: Troth, sir, nothing but what was concealed from myself—another daughter, who has an undoubted title to half...