The latest episode of "Reign" Season 4 is titled "Playing With Fire," and as usual, the episode is intriguing. The official synopsis of episode 4 says that Lord Darnley surprises Mary with a visit to Scotland, which makes her understand that their union is more than just a political bond. Elizabeth, on the other hand, acquired allies, and Catherine wants Claud to focus on securing a new husband.

The episode started with a couple of young boys fencing in the forest where they find Bianca nearly strangled to death. Narcisse and Catherine talk about how King Charles chose to bring Bianca to the woods to see the corpses of dead soldiers then bed her. Catherine denies that Charles is a necrophiliac, and they both agreed to stop this gossip.

Meanwhile, Mary is on vacation with Greer, Entertainment Weekly said. Mary refuses to talk about Gideon, and said that it is up in the air with Darnley. In the middle of their vacation, Lord Darnley appears. Darnley offers Mary a shoe which suggests that they marry, and Mary agreed that it would be good for Scotland.

In France, Catherine and Narcisse confront King Charles about how he treats Bianca, but Charles doesn't seem to care. This episode shows a lot of confrontations involving Catherine, as she is again involved in another argument between her daughters about their family. It ended with Claude being sent to the nunnery for her sins of the flesh.

The highlight of this episode is when a fire broke out. People started screaming "FIRE!" Darnley tries to remove Mary from the danger, but she said she must help them to save their crops. A.V. Club said that James helped fight the fire, and when it was finally put out, the villagers praised Mary, but James is suspicious.

When "Reign" Season 4 episode 4 was about to end, Greer tried to talk Mary out of marrying Darnley, but the latter said that it's the only hope of surviving Elizabeth. The episode concluded with Mary finding a letter that says, "Darnley started the fire to appear as a hero, signed by loyal watchman."