I find very little online about Carl Maldoner, except that he was an Austrian painter and a childhood friend of Sargent's. [sh]
[Sargent's] bravura portraits are also oddly closed. Their brushwork is so fluent, their light effects so dazzling that -- though we often glimpse a twinge of tension or self-doubt -- all that surface somehow blinds us to the contents of the sitter's soul. Sargent's, too, is hidden. He portrayed nude male models often, and a female nude just once, but if he ever had a love affair with man or woman, no trace of it survives.
...He who paints a tree may fiddle with the leaves, and he who portrays hands may elongate the fingers. But faces are unbluffable, and here Sargent excels. The blue eyes in his portrait of Carl Maldoner are so cold and so compelling they freeze you in your tracks....