'Reign' season 4 episode 4 spoilers: Will Mary trust Lord Darnley?

Promotional banner for "Reign" season 4 | Facebook/CWReign

Mary figures out if Lord Darnley deserves her trust on the upcoming episode of The CW's historical drama "Reign" season 4.

Titled "Playing with Fire," this week's hour will see the Queen of Scots face a new obstacle in her personal life. According to the official synopsis, Lord Darnley (Will Kemp) travels to Scotland to surprise Mary (Adelaide Kane) with a visit. Upon Darnley's arrival, Mary realizes that her union with him could be more than just political as he may be a suitable partner for her.

Meanwhile, Elizabeth (Rachel Skarsten) is still hell-bent on bringing her cousin down.To gain allies in her favor, Elizabeth is prepared to fight other groups. Elsewhere, Catherine (Megan Follows) is determined to get Claude (Rose Williams) back on the right path, so she attempts to find her a new husband.

It remains to be seen if Darnley will become Mary's next husband. As fans know, Mary has been betrayed by people in her inner circle before. It changed her perspective, and since the beginning of season 4, the queen has been wary of giving her trust even to those who are closest to her. However, if the series will follow the history books, episode 4 might also mark the beginning of Mary and Darnley's romantic relationship.

Spoiler reports note that Queen Elizabeth will do everything in her power to get more allies. Because she is intent on keeping Mary away from her throne, there are speculations that Elizabeth will not keep her end of the deal she made with Gideon Blackburn (Ben Geurens).

The CW has released a new promo for the episode, and it teases Charles' (Spencer MacPherson) dark secret. It is revealed that he is a necrophiliac, a person who does sexual acts with a corpse. "What are you doing? Answer me!" Catherine (Megan Follows) asks her son. The short clip also features scenes during Lord Darnley's arrival.

The fourth and final season of "Reign" airs every Friday night at 9 p.m. ET on The CW.