Morland Holmes's (John Noble) attacker will be finally exposed in the penultimate episode of "Elementary" season 4.

According to the synopsis for the penultimate episode, titled "The Invisible Hand," Morland's son Sherlock (Jonny Lee Miller) and his partner Joan Watson (Lucy Liu) will finally learn the identity of the person responsible for this attempted assassination. But the partners will be surprised to learn that the perpetrator is also linked to them.

Sherlock and his father have been estranged for a long time, until the older Holmes arrived in New York City to make amends with his son. But Sherlock found out that Morland only wanted to be close to him so he would protect his father from his mysterious executioner. This infuriated the detective, but he and Watson will still try to find out who wants to see Morland dead.

In the trailer for the last two episodes of season 4 shared by TVLine, the duo discovers that the perpetrator will stop at nothing to kill Moriarty. The culprit even uses a bomb to cause chaos. This makes Sherlock warier about the situation. When Watson asks him if he trusts no one, Sherlock tells her that she is the only person who earned his trust.

The synopsis for the penultimate episode reads: "When Holmes and Watson discover the perpetrator behind the attempt made on Morland's life, they find a shocking connection to themselves."

The episode airs on Sunday, May 1.

Meanwhile, the season 4 finale, titled "A Difference in Kind" centers on the threat against Holmes and Watson's lives as they come across a highly influential crime group.

The synopsis for the episode reads: "Holmes and Watson's lives are threatened by an influential, worldwide criminal network connected to the murder attempt on Morland Holmes. Also, Sherlock's grievances with his father threaten their alliance to bring their mutual adversary to justice."

The fourth season finale of "Elementary" airs on Sunday, May 8.