Squire Allworthy, a benevolent bachelor with a large estate in Somersetshire, discovers a newborn baby on his bed. He takes him into his care and names him Tom.  Shortly thereafter Allworthy’s sister marries the dreadful Captain Blifil, and they have a son, Blifil junior. 

Tom and Blifil junior grow up together.  Tom is bold, charming and always in trouble. Blifil is dull, dutiful and sneaky.  By the age of 18, Tom is ‘one of the handsomest young fellows in the world.’  The owner of the neighbouring estate, Squire Western, thinks him delightful.  Western’s only child, Sophia, 17 and gorgeous, falls desperately in love with him.  Tom, however, is cavorting with Molly Seagrim, a poor but pretty local lass, who soon falls pregnant. 

Sophia’s beauty and loveliness are irresistible, and Tom begins to fall for her.  He sets out to break the bad news to Molly, and finds her in bed with someone else.  He discovers that he is not the father of her child; indeed, she’s rather generous with her favours.  This frees him to love Sophia, but he has little hope of success with her.  He is after all a common bastard, with neither title nor fortune. 

Tom and Sophia are deeply in love, despite their efforts to pretend otherwise.  Sophia’s aunt discerns that she has lost her heart, but thinks Blifil is the cause of her sighs.  She informs Squire Western, who sees an opportunity to double the family fortune through marriage.  Blifil recognises the monetary advantage to be gained and immediately agrees to wed Sophia.  It’s all arranged – poor Sophia has no idea. 

Aunt Western triumphantly tells Sophia that she’s to be married to her heart’s desire.  Sophia, amazed and delighted, assumes her aunt is referring to Tom, provoking the family's fury. The Westerns are so horrified at Sophia’s attraction to Tom that they decide she must marry Blifil immediately.  Sophia pleads and weeps, but to no avail. 

When Squire Allworthy hears that Tom has designs on Sophia he is dismayed – one must know one’s station.  Blifil, who has been plotting Tom’s downfall most of his life, seizes the opportunity to feed Allworthy venomous lies, successfully persuading his uncle to cast Tom out. Bereft and abandoned, Tom heads off into the countryside.  The same night Sophia, doomed to marry Blifil in the morning, flees her family home and sets out for London.

By a quirk of fate, Tom and Sophia end up at the same inn.  On the way there, Tom happens to have saved one Mrs Waters from being ravished in the woods.  Mrs Waters is rather wanton and Tom is soon seduced.  Their tryst is interrupted by various mishaps at the inn, and it is soon common knowledge that Mr Jones and Mrs Waters are sharing a bed.  Sophia arrives in the dead of night.  Her elation at hearing that Tom Jones is staying under the same roof quickly turns to despair when she learns of his sleeping arrangements.  Devastated, she departs immediately, but she leaves behind a token so that he will know she was there.  On discovering it the next morning, Tom is inconsolable.  Determined to prove his love, he pursues Sophia across the country. 

Tom arrives in London just behind Sophia, but then has to use all his wits and charm to find her. Sophia’s protector, Lady Bellaston, meanwhile makes it her business to discover more about him.  She finds herself charmed, and decides to have Tom for her personal plaything.  She comes up with a nefarious plan to get Sophia out of the picture, and our poor heroine again finds herself being forced into an unattractive marriage.  But before it can be executed, Squire Western arrives in a cloud of chaos and fury.  He carries Sophia away with every intention of forcing her to marry Blifil.

Powerful people are now plotting Tom’s downfall.  He finds himself wrongly accused of murder and thrown in jail.  But Mrs Waters is his salvation.  She clears him of the murder charge and resolves the mystery of his birth.  A shocking secret is revealed, throwing new light on Tom’s future prospects. Sophia receives a third marriage proposal; this time, she happily consents.