1 - Darren lays down an info-dump. Let's say that he's trying to play it cool and act like this isn't a big deal - maybe moving to another area to search for the clock. At the very least, he's probably not making eye contact with Sarah.
DARREN (1): I believe its thaumaturgic properties could prove beneficial to my needs.
DARREN (2): You may recall how temporal events would occasionally be torpid or languid when in immediate proximity to the clock.
DARREN (3): If my calculations are correct, the application of a sufficient amount of energy should enable it to circumvent the limits of chronology entirely.
2 - Darren pauses, absentmindedly looking at a sword on the table. Sarah puts together the pieces and is rather surprised.
SARAH (1): Wait.
SARAH (2): You want to turn my clock into a time machine?
3 - Sarah's necklace goes from purple to black. She and Darren look at her necklace, fear creeping into their expressions.
SARAH: What have you done, Darren?
4 - A scream from off-panel grabs everyone's attention. Darren picks up the sword.