William Dane proves himself a heartless, underhanded, treacherous, and avaricious man.
When Silas Marner is a young man living and working as a weaver in Lantern Yard, he belongs to a tightly-knit religious community and becomes friends--or so he thinks--with another young man named William Dane. Silas engages in many religious discussions with William, who is
...given to over-severity towards weaker brethren...and holds himself wiser than his teachers.
When Silas becomes engaged to a young servant-woman named Sarah, he is relieved that she does not object to William's occasional appearances in his cottage so that the two men can conduct their usual discussions on "Assurance of salvation." However, one time at a prayer meeting when Silas has a "cataleptic fit," William, having witnessed this occurrence, intimates that this fit may well be "a visitation from Satan."
Silas, feeling bound to accept rebuke and admonition as a brotherly office, felt no resentment, but only pain at his friend's doubts concerning him; and to this was soon added some anxiety at the perception that Sarah's manner towards him began to exhibit a strange fluctuation between...shrinking and dislike.
Having begun his treachery, Dane furthers it to satisfy his avarice and his desire for Sarah. So, when the senior deacon falls gravely ill, William Dane capitalizes on his opportunity to rid himself of his rival as he and Silas take turns watching over the frail man at night. One night, as Silas sits by the bedside of the deacon, who has been recovering, he notices that the older man's audible breathing has ceased. Silas holds his short candle up and, shocked, he realizes that the deacon is dead. In fact, the deacon's limbs are rigid. Then, Silas notices that it is four o'clock in the morning and he wonders why William has not arrived for his turn of keeping vigil. As Silas steps out to seek help, several friends arrive along with the minister, but still there is no William.
It is not until six o'clock in the evening that William arrives, and he is accompanied by the minister because they have come to take Silas to Lantern Yard. There, an inquiry is conducted as the minister produces Silas's pocket-knife and asks the weaver if he knows where he has left it. Silas replies that he has thought it was in his pocket all the time. He is "exhorted not to hide his sin and to confess and repent" because the knife has been discovered by the deacon's bedside where the church money was laid, but is now gone.
Silas declares his innocence, suggesting that they search his dwelling. Further, the minister says that no one was with the deacon but Silas because Dane has declared that he fell ill and could not take his place the night before. Silas asks again that they search his house. But when the men do so, they find the empty bag hidden behind Marner's chest of drawers in his bed chamber.
A desperate Silas Marner appeals to the man that he has believed to be his friend; however, William betrays him instead as he pretends to exhort Silas to not hide his sin any more. Reproachfully, Silas asks Dane, "William,...have you ever known me to tell a lie?" But, the treacherous Dane accuses him of being in league with the devil.
Finally, lots are drawn and Silas is accused of the theft. He moves toward William Dane and says,
"The last time I remember using my knife was when I took it out to cut a strap for you. I don't remember putting it in my pocket again. You stole the money, and you have woven a plot to lay the sin at my door....there is no just God that governs the earth righteously, but a God of lies, that bears witness against the innocent."
In this despair Marner leaves and returns to his loom. Two days later, he learns that Sarah "held their engagement at an end." In a little more than a month, Silas learns that Sarah has married William Dane. Shortly thereafter, he departs Lantern Yard, where his friend has so sorely deceived him and dealt him such treachery.
William Dane is a terrible and extremely conniving person who will basically go to any lengths to get what he wants. He is one of Silas' friends and they actually meet because of their shared religious views and feelings. Their particular sect meets at "Lantern Yard" in a town in Northern England.
But unlike Silas, Dane's religious feelings only go so far as they benefit him directly. So when he sees an opportunity to enrich himself and get Silas' girl, he manages to work out a plan to do both. He has a pile of money stolen from the church, gets Silas blamed for it, then runs off with his girlfriend and ends up marrying her.