Conrad Veidt did not receive an Oscar nomination for portraying Captain Hardt in The Spy in Black.
Conrad Veidt plays the German submarine Captain who attempts to carry out the central plot with the help of another German agent posing as a school teacher Frau Tiel played by Valerie Hobson. Veidt and Hobson would team up again the very next year, along with director Michael Powell, this time as two people trying to stop German agents in Contraband. With Contraband and The Spy is Black it is quite interesting to examine Veidt as the leading man to begin with. He's more than a bit atypical given his rather evident German accent. Veidt plays the lead here who technically should be the villain since he's playing the German agent during wartime in a British film. Veidt's a fascinating performer to watch as he actually fits what should be the standard structure of the villain. He's got the mandatory German accent, he's physically imposing to be sure, and Veidt never intentionally subverts his character's position in the way you might expecct. He's obviously believable as the enemy agent, and one should never question his possibility for danger yet even though he is in fact working for an evil regime Veidt prevents Hardt from really being evil.
A great deal of this comes from Veidt calling upon perhaps his greatest asset as a performer his oh so expressive eyes. In the early scenes just as he's being given his marching orders to go about the task Veidt so effectively realizes a hesitation in the man, which he never needs to verbalize this in his performance. Veidt is rather brilliant in that he really somehow is very charming yet never compromises the status of his character. it seems almost intangible in way as Veidt makes Hardt innately likable, though I do think again in those eyes, which made his performance in The Man Who Laughs so special, there is such a genuine humanity. Veidt though importantly is able to remove the result of the act from the motivation of Hardt. Veidt in his performance never makes Hardt seem sadistic in the plan, but rather keeps the drive of the man particularly straight forward. This works in creating the sense that Hardt's not working in any personal malice, but rather simply is doing his duty as a German Captain. The funny thing is Veidt so well reveals these motivations in Hardt that he not only stops him from seeming just as the villain of the film, but also does something that seems more impossible which is to make the German spy rather endearing.
He is helped along by the film to a point as Hardt purposefully dresses as German officer to not be seen as a spy and even questions the less merciful methods of his associates. Veidt makes the most of these moments as he delivers a considerable passion in Hardt as well as a definite disgust as he questions the murder of a civilian. What's pivotal in Veidt's depiction of Hardt comes in with his relationship with apparent fellow spy Tiel. Veidt and Hobson strike up a terrific dynamic with one another, and she helps to make Veidt seem all the more delightful by being so cold herself. The two have rather astonishing chemistry with one another as they manage to develop a romance of sorts between the two despite the certain hostility set between the characters in addition to the fact that little time is devoted to this element. Veidt and Hobson though are able to convey this in just a few pivotal glances and moments that results in something rather special. Now the film's spoiler twist ending comes as it is revealed that everyone besides Captain Hardt is in fact a British agent, and why they don't merely arrest Hardt from the get go is not particularly well established. The film should completely fall apart at this point given how sizable of a plot hole it is, but I still found the film ended up working thanks in large due to Veidt. He stays compelling to watch and so honestly finds the nature of Hardt that he makes it difficult to sympathize with him as he attempts to make his escape. The film even seems to position firmly as the villain at this point yet Veidt never compromises giving a very moving depiction of a Hardt's desperation as his plan falls apart. It's incredibly strong work from Veidt as he really does carry the film past being a spy thriller, where it probably would have failed if that's all it was, through his portrait of a decent man forced to fulfill a terrible duty.