Question: What type of stories did the author of the 1938 novel This Man Must Die use the pseudonym of Nicholas Blake?

Context paragraphs:
Man Must Die: Man Must Die is a Scottish technical death metal band from Glasgow, formed in 2002.

Dorothy Must Die: Dorothy Must Die is a 2014 young adult book by Danielle Paige and her debut novel.  The book, which was produced through Full Fathom Five, was released on April 1, 2014 through HarperCollins and was preceded by the novella "No Place Like Oz".  "Dorothy Must Die" is the first book in the "Dorothy Must Die" series and The CW is currently in negotiations to produce a television series based upon the series.

No Tolerance for Imperfection: No Tolerance for Imperfection is the third album by Scottish technical death metal band Man Must Die.

Cecil Day-Lewis: Cecil Day-Lewis (or Day Lewis) (27 April 1904 – 22 May 1972), often writing as C. Day-Lewis, was an Anglo-Irish poet and the Poet Laureate of the United Kingdom from 1968 until his death in 1972.  He also wrote mystery stories under the pseudonym of Nicholas Blake.  He was the father of actor Daniel Day-Lewis and documentary filmmaker and television chef Tamasin Day-Lewis.

The Beast Must Die (1952 film): The Beast Must Die (Spanish: "La bestia debe morir" ) is a 1952 Argentine thriller film, which is directed by Román Viñoly Barreto and stars Guillermo Battaglia, Narciso Ibáñez Menta and Warly Ceriani.  It based on the novel The Beast must Die by Irish poet Nicholas Blake.

...Start Killing: ...Start Killing is the debut album by the Scottish technical death metal band Man Must Die released in 2004.

This Man Must Die: This Man Must Die (French: Que la bête meure ), American title The Beast Must Die, is a 1969 French and Italian thriller film directed by Claude Chabrol.  The story is based on a 1938 novel by Cecil Day-Lewis, writing as Nicholas Blake, "The Beast Must Die".  The film had a total of 1,092,910 admissions in France.

Peace Was Never an Option: Peace Was Never an Option is the fourth album by Scottish technical death metal band Man Must Die.

The Human Condition (Man Must Die album): The Human Condition is the second album by Scottish technical death metal band Man Must Die.

Orcs Must Die! 2: Orcs Must Die!  2 is a trap based action-tower defense video game that Robot Entertainment developed as the follow-up to the original "Orcs Must Die! ", with Microsoft Game Studios publishing the sequel for the PC on July 30, 2012 in the United States.  On April 2, 2012, Microsoft announced the development of "Orcs Must Die!  2" at the Penny Arcade Expo in Boston (PAX East), with their emphasis on co-operative gameplay as the principal addition over the original.

Supporting paragraphs: This Man Must Die Cecil Day-Lewis
Answer: mystery stories