The sentence as written has suspicious modify walked in an attributive fashion—somewhat unusually, since it's being used (syntactically) adverbially rather than adjectivally. Suspicious, unlike the actual adverb suspiciously, is a noun, but, in this syntax, it's still modifying the nature of how Marlon is walking. (Even though it shouldn't be. Any modification of a verb in a construction like this should be done with an actual adverb, not a noun.)
The common way of writing this is to make suspicious nonrestrictive (and adjectival rather than adverbial), as in the following:
Marlon walked, suspicious, along the corridor.
The parenthetical commas serve two purposes:
They make it clear that suspicious is not acting restrictively to modify anything about the sentence.
They allow the noun to act as a noun, modifying (attributively, as an adjective) Marlon himself, rather than his walking (adverbially).
An alternative way of writing this, but one which is not as common, is this:
A suspicious Marlon walked along the corridor.
Such a style of phrasing is certainly used, but it's not very common. However, that doesn't make it wrong, and it might fit the rest of the narrative style. It would be up to context and personal choice.
Also note that in this variation, suspicious is explicitly adjectival as well as restrictive.
As mentioned in a comment under the question while I was writing this (I had not thought of it myself), you could also use suspicious as an introductory clause:
Suspicious, Marlon walked along the corridor.
And some additional variations from comments to this answer:
Marlon, suspicious, walked along the corridor.
Marlon walked along the corridor, suspicious.