When exactly does the Time Stop spell end if you affect a creature or object while time is stopped?

Question

This question concerns this sentence in the time stop spell's description:

This spell ends if one of the actions you use during this period, or any effects that you create during this period, affects a creature other than you or an object being worn or carried by someone other than you.

When exactly does the spell end? Before the action or effect affects the creature, or after it affects the creature?

Here is the specific situation I am thinking about:

Alice is attempting to steal an object off of Bob's person. Alice casts time stop and begins to go through Bob's pockets to find the object. Can Alice use her action to search Bob, find/take the object, and use her movement to run away before the spell ends?

Would this be a valid ruling, according to the language of the spell?
If not, what is the correct way to resolve this?

Answer 1

It’s up to the DM.

For a lot of the actions you can perform in combat, such as attacking or casting a spell, it’s pretty clear when your character is affecting another creature. But these aren’t the only things you can do in combat. As it says in the Player’s Handbook:

Your character can do things not covered by the actions in this chapter, such as breaking down doors, intimidating enemies, sensing weaknesses in magical defenses, or calling for a parley with a foe. The only limits to the actions you can attempt are your imagination and your character’s ability scores. See the descriptions of the ability scores in chapter 7 for inspiration as you improvise.

When you describe an action not detailed elsewhere in the rules, the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure.

It’s up to the DM to determine what constitutes affecting another creature, especially if what you’re doing is something like what is described in this paragraph from the PHB.

In the scenario you give, I would rule that the spell ends the moment Alice touches Bob. That said, because of time stop I would rule that Alice need not make a stealth or sleight of hand check, rather I would allow her to make an investigation to check to find the item she is looking for.

To be clear, there is no clear cut way to rule this. Time stop can create complex scenarios that the general rules are not really prepared for, so many of the interactions with the spell are going to require a DM ruling. Another DM may rule your scenario quite differently, and that would probably be entirely reasonable.