彼がどうやって逃げたか全くわからない。

he; him; his; boyfriend

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

how; in what way; how about

to do; to undertake; to perform; to play (a game); to study; to send; to dispatch; to despatch; to put; to move; to turn (one's head, glance, etc.); to give (esp. to someone of equal or lower status); to let have; to present; to bestow; to confer; to make (a vehicle) go faster; to run (a business); to keep; to be engaged in; to practice (law, medicine, etc.); to practise; to have (food, drink, etc.); to eat; to drink; to smoke; to hold (a performance); to perform; to show; to ease (one's mind); to harm; to injure; to kill; to have sex with; to live; to get by; to get along; to do ... completely; to do ... broadly; to do ... to a great distance; to do ... for (someone of equal or lower status); to do ... to (sometimes with negative nuance); to make active efforts to ...

to escape; to run away

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way

really; truly; entirely; completely; wholly; perfectly; indeed; good grief (expression of exasperation)

to understand; to comprehend; to grasp; to see; to get; to follow; to become clear; to be known; to be discovered; to be realized; to be realised; to be found out